Coalitional motte-and-bailey has both motte-defenders and bailey-promoters as distinct groups. The motte people can tacitly disagree with the bailey claims, avoid motte-and-bailey dynamics within their castle, regard the bailey people with some distaste, and dislike when some of their own start presenting at the bailey events. At the same time, the bailey people advance their wild claims while gesturing at the motte arguments (which they often don't understand) and the prestige of the authors of the arguments, which directs attention and public renown to the motte people. The latter sometimes indirectly creates opportunities for the motte people to gain prestige and funding within the castle.

So I think motte-and-bailey often isn't about any given person retreating to a more defensible claim, it's not about changing the topic or giving a misleading impression. The motte people (generalized priesthoods) are usually not themselves bailey-promoters at all, and the bailey people are often unable to personally retreat to something legible, even when they bother to. It's about a conflationary alliance between groups that fill different roles in the superficially incoherent whole, which functions well enough to perpetuate itself.