This is because the naive mental model of development processes is bullshit: the techniques introduced and used should never be some rigid dogma. This applies to "agile" or whatever flavor-of-the-year we're talking about.
Agile is best thought of as an ecosystem of tools used to shape software (and knowledge) work. Am I "doing it wrong" when I get out my toolbox, use the #2 Philips head screwdriver, but not the torque wrench? NO! Not if I didn't need the torque wrench!
And that's a massive source of pain with "agile", or what I think of as "kitchen sink agile" where the goal becomes, explicit or not, to apply as many processes from as many books as possible – instead of picking just the right ones.
I've literally never been on two teams with the same process needs in my entire (now long) career. Even those teams year-over-year evolve their needs as the members, organization, and business change. Why should the process therefore be a static entity? One of the very few fixed rules I've learned hits to the GP's theme: it's critical to have the least necessary process, just as it's ridiculous to break out every tool in the box just to tighten up a loose screw.