Actually it could be correct. Like he said, most companies use the same shell for each half size and only change the liner (so a 27 and 27.5 of the same boot would have the same BSL). Having said that, BSL changes between boot manufacturers. My old Garmont touring boots were 27 shells (actually 'size' 27.5) and had a 306 BSL. When I upgraded to Dynafiddles, I went down to a 26 shell with 302 BSL because the 27 shells had a BSL of 312 mm.
I hope that made sense how I explained it. Basically, if OP changed boot manufacturer then he should take the stuff to a tech to adjust the binders (and they shouldn't have to remount...just move the heelpiece accordingly), but if he stayed with the same manufacturer then there is a decent chance that the BSL did not change and he would be fine (assuming the binders were correct beforehand).