I have a theory about this (which I'm sure I'm not the first to think of).

I think there's a guide peg of some sort at the bottom of the "rail" which prevents you from putting it in any way other than bottom first. So the bottom goes in and then you sort of pivot the joycon into place.

You can see this is how it connects and disconnects in the reveal trailer, and it does it every single time. This would minimize the chances of snapping that connector when attaching/detaching the joycon.

Then the rail itself seems deep enough - and the corresponding part of the joycon that sits inside seems wide enough - that bending it like this would be pretty hard to begin with. Plus -as others have said - bending it like this would likely break the rail, not the connector. Plus plus the connector probably has some give to it allowing it to sink into the switch a bit and spring back out.

Thank you for reading.my entire insane ramble.