I genuinely hate the dishonesty. Why is it drilled in people to fake being nice? Why does one have to be so polite? There are ways to say no and still be polite. Or just simply say, hey thank you but I'm not super interested. Idk man. I'd rathe have a no than a maybe (probably not).
I think there are two ways of being polite, one is that fake-politeness you mention, the other is more of an avoidance of proactively hurting people's feelings.
As an example let's say you think gender reveal parties are stupid. Your friend invites you to their gender reveal party for their baby. Declining the invitation with a fake excuse is the first kind of polite. Just declining by saying you don't want to go is the second. Proactively offering your opinion that gender reveal parties are stupid in general and your friend shouldn't have one even though they didn't ask and probably already scheduled it would be unnecessarily hurtful. On the other hand if they asked you what you think of gender reveal parties instead of inviting you I would not see it as rude to respond honestly. Also, if you decline politely and they keep probing deeper for reasons you are under no obligation to make up some fake reason.
I guess I have trouble telling which level of masking I'm seeing talked about because I interpreted the op as a conscious thing whoops.
I do both levels. Like, I have "I don't want to explain this thing" which I'm trying to stop on that conscious level, but I also experience the other side where certain circumstances are just like, flashes in my brain that pull out the only response that feels safe, or sometimes the only one that seems non-destructive, but not in a way that I'm capable of processing in the moment, and I don't know why I do it often. Unraveling that is a lot harder, though, and while it is happening, maybe the less advanced state of that unmasking effort is also why I can't see it being talked about.
My problem? The next day, I've completely forgotten about the conversation and the event. So it's an hour before the thing, I remember there even was a thing, then don't go.