Personally I'm willing to have a little suspension of disbelief. Things like the ropes being too tight to be safe in real life, having someone restrained for days at a time with no ill effects, and the like are details I'm willing to gloss over under the idea that it's fiction. Kinda like how plenty of stories ignore details like the 'lee growing desensitized from extended tickling. It's more about the fantasy of the scenario, in many cases because it's unrealistic instead of in spite of it, than trying to write about a realistic session.
With that said, there does reach a level where it does take me out of the story. Like in the example you mentioned, having a lee hanging by their ankles makes me more go "That sounds painful" than "That seems like a good position for foot tickling" when I try to imagine it. There's a certain point of what's being written being so far outside the bounds of what I can conceptualize that my brain gets tripped up on that detail and it becomes hard for me to imagine the scene without some part of me balking at how there's something wrong with it.
