Gavin, it is different. What you are suggesting is paying for a fifth year to do general dentistry, like a fifth year of dental school. I know you are in support of this, but this isn't really an issue of mandatory fifth year or not. It's more about access to care and being treated like a resident (because you are a resident). With the slashing of GME funds, many programs will be in limbo about staying open or will have to reduce their patient load, denying dental care to those who can't afford private office treatments.
Dental school is 4 years long. If you choose to specialize, looks like you'll have to pay tuition for the majority of programs (minus OMS & some pedo). Fine. That's how it used to be and now we're going back to that. Some specialties are pretty cushy programs anyways (like you get all the school holidays and summers off), so them being paid as residents these past few years made it that much more cushy. (As compared to their GPR or OMS/Pedo counterparts where you don't get that 2 week break between Christmas & New Year's and no way are you gonna get the entire summer off).
But, if you're headed for general dentistry and you want to do a residency or "fifth year" - where are you more inclined to go? The program where they pay you (GPR) or the one where you pay them (AEGD programs losing their funding). Basically where you pay them, it's like a fifth year of dental school. You are paying to be a resident in general dentistry. I think very few seniors will choose this route, when the options right now include do a GPR instead, or go straight to private practice and use your money to pay for CE courses instead. For example, if you really want to learn all about implants, paying to attend an AEGD for 1 year is not necessarily going to make you as proficient as coughing up the money to go to a serious hands-on CE seminar on doing implants. At the AEGD, you have to do all phases of dentistry, you can't just do implants even though you paid to go there.
Right now, as first years, you are inclined to be very excited about learning anything dental to get your mind off the muscles of the arm or pathways in neuroanatomy. You're ready to commit to anything to get that DDS. But as a senior, I've had it. I've earned the DDS, the school is just seriously hazing me this year before actually giving me the diploma in May. There is no way I'd go through this for another year of general dentistry and lose more money in the process. GPR, get paid for it, serve the community, yes. AEGD, pay them for another year of "dental school," no.