More info. I did a manual upgrade and used pkg_add -u to update firefox-esr. I removed the package and reinstalled. Recursively deleted ~/.mozilla and firefox-esr now correctly ID's as OpenBSD - 7.5
I was initially concerned that the build info had not been updated. For some reason pkg_update did not replace the package for 7.5. I expect this will correct in 7.5 on the next firefox-esr update. Regards --- J. Scott Heppler