I think it depends how well you know your fellow riders - I know no one I regularly ride with in the club would brake if they got a flat when they know someone is behind them but also most of them use tubeless which doesn't tend to deflate quickly when you get a thorn through it. But if it's a less regular group then you can get erratic behaviour - a guy in front of me on the commute recently suddenly veered away from the bike lane / kerb at 40kph and I was presented with the back of a runner who had stepped off the pavement into the road. I had maybe a second to react and must have missed them by less than an inch. The other rider knew I was there too and should have known that the runner might be about to do that because a car pulling out of a drive was blocking their way, but clearly not too bright. Some wheels aren't worth drafting.