Sidious66's interpretation is pretty persuasive and I'm not sure anything has been offered to contradict it.
We know Sheev was able to project his essence into the clone body on Exegol en route to the Death Star reactor core:
From that same passage, we know Sheev's acolytes were seeking a superior "cradle for their god-consciousness" and this quest produced a number of "unnatural abominations" to serve as "a worthy receptacle."
That same passage explicitly says "nothing worked," despite The Star Wars Book explicitly referring to Snoke as one of the strandcasts created as a result from this process:
Yes, Snoke was physically impaired... but obviously, clearly far less impaired than Sheev's "rotting corpse" of a clone body that required an Ommin harness and alchemical fluid to keep him functioning.
So, to recap:
* Sidious has the means to project his essence at whim into a blank receptacle without need of the STRIKE ME DOWN IN HATRED ritual
* Sidious was looking for a better body to cradle his consciousness
* This search was determined to be a total failure, despite the effort producing Snoke
* In terms of health, mobility, and stature, Snoke's body is objectively far healthier than the rotting clone corpse Sidious currently occupies
* Sheev has a giant jar of pickled Snokes on hand
This pretty clearly indicates Snoke is not a viable phylactery for Sheev's soul. He's not strong enough and we have no reason to believe otherwise.