I was about to laugh too 
You hinted to the reason though: if someone is just crossing over, and sees Boston Lager as their "stepping stone" beer, once they get full-on into craft beer it is easy to think that Boston Lager tastes different.
There has definitely not been a change to that beer in years. BUT, it is one of those beers that tastes totally different from a bottle than it does on tap (it's always been that way).
You hinted to the reason though: if someone is just crossing over, and sees Boston Lager as their "stepping stone" beer, once they get full-on into craft beer it is easy to think that Boston Lager tastes different.
There has definitely not been a change to that beer in years. BUT, it is one of those beers that tastes totally different from a bottle than it does on tap (it's always been that way).