This is on the APPIC website:
***Waiver
The Family Education Rights and Privacy Act of 1974 (FERPA) gives you the right to access recommendations unless you choose to waive your right of inspection and review. Prior to requesting any recommendations, you are required to indicate whether you wish to waive your rights. AAPI will release your decision to waive or not waive access to your recommenders and designated programs. Your waiver decision serves the same purpose as a legal signature and is binding.
Selecting Yes indicates to programs that your recommender completed their recommendation with the understanding that you would not be able to view it. This means you will not be able to see the content of the recommendation. Programs may view this type of recommendation as a more accurate representation of an applicant's qualifications.
Selecting No indicates to programs that your recommender completed their recommendation with the understanding that you may choose to view it in the future. Selecting this option does not allow you to view your recommendation via the application. If you do not waive your right to view the recommendation, you may ask your recommender for a copy of the recommendation. Programs may view this type of recommendation as a less accurate representation of an applicant's qualifications.
Once you make a selection, you can't change it, so consider the choices carefully.***
I was in the same boat back when I applied for internship. I had an awesome DCT who offered to review letters of recommendation for all recommenders because recommenders may not be familiar with what APPIC sites are looking for. I shared my particular concerns with my DCT about my PhD advisor because my advisor wrote me a not-so-good letter for practicum applications (they complimented me in a unique way, which may not be viewed favorably unless you know them). They ultimately did let my DCT review their letter with the same issues I noted before (since they used the same letter) and my DCT gave them feedback. I waived my right to see his letter back then, but when I requested another letter for postdoc applications, I did see a good revised letter. I know DCTs are busy but I wish more DCTs would/could offer to do that.
It is probably late at this point, but if possible you can request additional letters from other recommenders and assign them to different applications. I requested 5 different LORs for internship applications and did not use my advisor's letter except for the sites that specifically required it (since I could not read it to be sure it was good and knew what every other recommender wrote). However, you pretty much have to submit your advisor's letter to research-heavy sites. Some sites I've been at also view LORs more qualitatively instead of including them as part of the metrics. One less-than-stellar letter probably wouldn't hurt you as we understand it is often out of your control how well those letters are written and it is only one of the many data points you are assessed on. Individual supervisors may also place more emphasis on different aspects of your application. So I wouldn't be too worried about this.
I agree with futureapppsy2 that we can be more upfront about what we are looking for in an LOR and make sure it is an excellent one before it is too late. It is important to remember that even though they say all these nice things about you in person, they may not necessarily translate those words into a letter (supervisors whose letter writing lacks quality and/or quantity or who are just spacey) even if you specify what you are looking for in their letter. The good ones will give you a draft ahead of time to make sure it includes everything and give you the opportunity to edit (e.g., reminding them about certain experiences you had with them). Postdoc application procedures vary a lot from utilizing a universal portal or an institution-specific portal to submitting everything via email (directly from supervisors or by you). One of my spacey supervisors actually rewrote my letter with a lot of missing details instead of using an old recommendation letter (which was shared with me before). I was lucky to have applied to sites that required email submissions by me and read the letter even though they had submitted it to two of the sites (one of which still interviewed me and offered me a postdoc). I reached out and asked them to add details based on the previous letter before they submitted it to other sites by themself. Just something to keep in mind if you feel these LORs are really important.
