See this thread where I rant about the carriage being incredibly out of wack on my machine: Carriage Tolerances - Unusable Over Distance >75mm From Center. There’s no chance I get a successful alignment using the bed, or webbed carriage. I’d have to use the Y axis module mounts, but they are hard to get to without disassembly - by using the case of the module it’s a quick and easy check I can do frequently without disassembly.
Never. That sounds very not good, and would explain your print issues in the other thread, also. If only 1 tower moves, that leads to all sorts of issues.