You understand correctly. I had an open VFR flight plan w/ SE-SAR, but being my first real solo cross-country, I decided I wanted flight following as well. So I hit up the approach controller with a vfr flight following request, got assigned a couple of different squawk codes for coordination with center. Then a different controller on freq asked me for my final cruise altitude. I provided it and she cleared me into the bravo and gave me climb instructions and a vector. I accepted the clearance when I should have replied "Unable" and explained that I was a student w/o endorsement for the Class B and needed to stay clear of the Bravo. However, I usually fly out of a Class D with radar coverage and am relatively used to traffic advisories and basically doing whatever ATC says as long as I don't see anything outside or on ADS-B that would make me worry. After a few minutes in the Bravo on assigned heading, I was cleared on course and within another minute or so was under the outer ring of the Bravo again and handed off to Center for continued flight following.
After I got home, I checked the FAR to validate that I screwed up--I couldn't recall with certainty if it was landing at a Class B airport or entering Class B airspace entirely that needed an endorsement. I filed an ASRS report more as a CYA than anything else, as safety was never really at issue.
