No, its true no matter what.
ECs shouldn't be to "get into medical school." I have plenty of friends who will never apply to med school or grad school, and they still had jobs, volunteer positions, and were active in other things. Its called being well rounded and having interests other than academics.
I think even you would have problems if you don't have anything prior to your senior year. It makes your GPA look less impressive because you had so much free time, and it leaves you with nothing to make yourself stand out against the average applicant. But you don't have that problem, you had a job before you decided on medicine - thats an EC. The OP has nothing from what he's saying - thats a huge issue.
I wasn't sure I wanted to go into medicine my first or second year of college. I didn't make up my mind until the summer after my junior year. I still had a job all 4 years, volunteered in a free clinic because it was interesting and helped me figure out if medicine was for me, babysat, worked at local middle schools, etc. I did it for me. Not for med school apps. Just like you worked for you, not for med school apps.
Sadly, in this day and age most ECs are just "for" med school. But they shouldn't be. And saying "I wasn't sure I wanted to go into medicine until later" isn't going to explain a complete lack of ECs early in college, it may explain a lack of medically related ECs. (but you said you worked so you're probably fine) But it never looks good to be doing nothing but school, whether you're premed or not.