I've had difficulty understanding the 5th of the 5 these of Mahadeva, i.e "the path is accompanied by utterance."

In a 1978 issue of the JIABS, the following is provided in an article on the Mahasamghika and the doctrine of Tathagatagarbha.

The fifth of these seems explainable by other Mahasarnghika tenets, in Bareau's listing:No. 58 'morality is not mental'; No. 59 'morality does not follow upon thought'; No. 60 'virtue caused by
a vow increases'; No. 61 'candor (vijnapti) is virtue'; No. 62 'reticence (avijnapti) is immoral.'

Does this suggest that what looks like morality for an Arhat (assuming this thesis is valid), is actually compliance with the instruction of an external agent rather than internally motivated?