Ignoring HOLDDATA instructing me to do so, is there a specific module that would be modified by maintenance that should signal me that I need to write IPLTEXT to my IPL volume?
I typically just see if SYS1.NUCLEUS gets modified and write IPLTEXT regardless, but I wasn't sure if there was a 100% reliable way to know in case the HOLDDATA neglects to mention it.
There's a wait state 019 that I only saw once in my career when a sysprog accidentally pointed their ICKDSF IPLTEXT JCL to SYS1.SAMPLIB on the previous OS level instead of the new OS level. So other than that mistake, I don't think the system will complain at IPL time about other possible updates, which I think is what you are addressing.
What about checking SYS1.SAMPLIB(IPLRECS) and SYS1.SAMPLIB(IEAIPL00) for updates, which (unless things have changed since I last wrote out IPLTEXT) are the source for the IPL records on the res pack?