I don't agree. Being put on the spot is the fault of the one asking, not the receiver.
Maybe saying,' you've put me on the spot there so I'll get back to you asap,' might make the asker realise they may not have considered the consequences of asking for something that isn't easy to give.'
Recently we had the term, 'that's a big ask', whilst I didn't particularly like it, at least it reflected the complexity of some situations.
I had a message to meet up for coffee yesterday. I jumped at the offer but realised I didn't have my car.
I accepted then stated I needed a lift to which the reply was to confirm I would be picked up at a certain time. I did realise, though, that I might have to turn it down if there was no lift available...
Maybe it's me but I always have a contingency plan if the person I'm asking can't help me out...