Arturo started playing better in SF4 after spending a lot of time in UNIEL. Chris G started doing better in SF4 while he was at his best in MvC3. Sonic Fox plays multiple games and continues to get stronger. Tokido had his highest placement at EVO in SF4 while also placing in KOF13. Hell, look at Tokido's EVO record and he's placed in Guilty Gear, Virtua Fighter, Street Fighter, Blazblue, CvS, Tekken, SFxT etc. Someone playing all those games and being one of the most threatening fighting game players of all time must pick up things from different games.
Everyone gets something different out of playing other games and no one game is the be all and end all of how to become a better fighting game player as a whole. Just by playing other games you'll get a different perspective and approach which will build upon your own abilities. Getting all worked up over one comment just isn't worth it, especially when you know that it's something entirely subjective as it is.