Actually in the case of Sam, they've showed him shirtless or put him in storylines where his physical attributes are supposed to be a big deal quite a few times, even starting back in Season 2. The Rocky Horror Picture Show with the gold shorts and than in "Never Been Kissed" explaining to Finn how he needs to work to maintained ripped (while shirtless naturally) in the locker room. Segue to Season 3 and being a teenage stripper and then his "sexy" moves for a competition performance. Let's not even go with Season 4 and Season 5 with "Naked" and "junk the size of car".
Plus in the context how little they showed the God Mike Chang (aka Harry Shum Jr.) shirtless , yeah, it's been quite numerous.
It's more that the show constantly pushes how "hot" Sam and Blaine are. It becomes overkill when they just repeat that over and over. Similar to how Glee pushes how Rachel is the most talented Broadway bound singer on the planet, after awhile you start noticing things. With Rachel I start to notice that yes, she's talented, but no, she's not head and shoulders above every else.