I wasn't aware the OCLP OS installer patched anything
I would have thought this would be apparent from the OCLP name, as "P" stands for "Patcher".
In any case, OpenCore as a whole is a patcher. The thing about OCLP is that it makes additional filesystem changes AKA
Rigid Patching
while plain OpenCore only does
Soft Patching
(RAM only). The issue, and ConfigFactory tries to work around this to an extent, is that patches can conflict.
This is explained in ConfigFactory when you select the correct response to the query on whether you intend to use it with DosDude Type stuff. Not sure if still in the CDF guide but it warned against using it with such rigidly patched instances.
It could be that OCLP rigid patching is a specific additional option that is not always used though. I am pretty sure it is difficult to avoid for Monterey but could be wrong.
some of the recent MyBootMgr OC configs definitely worked OK with it as do CDF guide and Martin Lo configs.
Possibly so indeed. You will note I didn't say that the chances of success are zero but "slim".
FWIW, I have also consulted OpenCore's developer on your issue and his conclusion is that it must be due to something done by the OCLP. This was admittedly from a quick look at the log but either way, there is little point trying to troubleshoot failures with a known incompatible setup. To use OCLP instances with MyBootMgr and be sure of success, you need to manually incorporate it as a separate instance. See Post 1 for details.
However, you can always toss a CDF config in again and see if it still works. If it does, then the MyBootMgr one should also do so if you compare it with the CDF one and disable any additional kexts and patches until you have disabled all such extras or stumble on one that is in conflict with OCLP.