A gap between "this is how the designer wanted this mechanic to be used" and "this is what the mechanic's design actually encourages players to do" is one of the hallmarks of flawed game design. For all the bold assertions of pragmatism that come from amateur-designer DMs, there is a rather strange trend in TTRPG design to emphasize that designer intent should always be what matters most. That users who don't follow that--regardless of why they do so--are the ones at fault, not the design or designer. It's very frustrating.
In this case, the ideal is certainly that the DM should only be using Intrusions because they make the game better, and never do so when they wouldn't make the game better. Unfortunately, I find that a lot of DMs don't actually know how to do that, and indeed have a lot of mistaken but entrenched beliefs about what leads to better gaming. As was said earlier, the gap between "this is something the player explicitly opted into in advance" and "this is something the DM forces, and extracts a price if refused" is pretty big, and there's quite a bit of room for resentment or frustration even if the DM genuinely believes what they're doing is good.