Explainpaper for the specific frustration of a sentence you cannot get past is exactly the right use case
That specific frustration, understanding a paper you mostly understand except for one technical section, is where Explainpaper's design is actually calibrated. You are not trying to understand the whole field. You are trying to understand the three sentences that are blocking your comprehension of a paper you are otherwise following.
The level of explanation selection, the video mentions graduate level as an example, is what prevents the explanation from being condescending to someone with domain knowledge who just needs the specific technical term clarified rather than the whole concept re-explained from first principles.
The follow-up question capability within the highlighted section context is the chain that lets you go from the initial explanation to the next unfamiliar term it introduced without losing the context of what you were originally trying to understand.
For researchers using Explainpaper regularly: is it primarily for reading outside your specialisation or do you find it useful for catching up on developments within your own field where terminology has evolved?