I wouldn't ignore the warnings! Suppose I had a Glock Gen 1 .40. That chamber isn't very well supported. Or course, I am guessing that there is actually a Gen 1 .40 - I wouldn't know. Sometime back, actually, a long time back, there was a problem with Glock .40s.
But it IS a fact that there are still Glocks in circulation where the feedramp seriously undercuts the chamber.
I would check my chamber by dropping a round in place and see what I thought about the support of the case near the feedramp.
Somebody on this forum posts photos of the various barrels and I know I have seen similar photos in General Glocking. A forum search will probably turn up something.
There's a reason the warnings are there. For newer models it may not be an issue but it certainly used to be a problem. As the warnings are only related to .40, it is also apparent that the folks writing the manual knew exactly which guns had the defect.
"No matter how cynical you become, it's never enough to keep up." - Lily Tomlin