Should SE scale high end content difficulty towards the usage of SIM ?

[Valence]

Not really. The ability to practice a later segment of something in isolation without having to go through the whole thing to get there is always advantageous. This applies to literally anything, not just raiding. It's no different from a musician practising a passage from the end of a difficult piece of music on its own.

Then the question becomes, why are checkpoints not an option?

( the answer is pretty obvious )