When fixing T243590 it was highlighted that some DataModel hashes are calculated from PHP serialize and unserialzie methods.
Generally speaking, these hashes are meant to be stable and should not unexpectedly change.
The PR fixing the tests added a stability check for the hash of the ReferenceList object, and while looking around the code a few other stability checks where also spotted.
To be sure we should audit the code and add tests for stability for all gethash methods