Both MCS and PSR are comprehensive in their class docs and it doesn’t look like there are conflicts. It looks like current MCS is a subset of PSR. 

However, this should be reviewed more closely to make sure nothing has

MCS: https://moodledev.io/general/development/policies/codingstyle#namespaces 

PSR-12: https://www.php-fig.org/psr/psr-12/