I've navigated this a few times. The way I've explained it is I say I've started to develop "some" feelings and I asked if they have any of the same feelings. I confirm that it's absolutely something I can control and end, but brought it up asap to know whether not to do that.
idk how to explain that 7 times out of 10, it’s basically a friendship-ending event. people prefer the status quo, if your counterparty gives you an “escalate or we’re done” ultimatum, a lot of people are gonna react negatively to that. men don’t seem to have a problem understanding this dynamic in reverse, for example, when marriage proposals are expected