Well, if you actually read what you googled then linked, it says in there about the dangers of low charges of slow powders.
For a start, SEE, secondary explosive effect
If you read up any of the trusted and tested sub 308 loads, they use small charges of fast (pistol or shotgun) powders. The problem with this, is double charges are hard to spot, which is why trailboss is great, as it's so bulky. And, very easy to work down to subsonic loads without starting too high.
H4895 can be used for 'reduced' loads of 60% of listed max (less 10% of that load if needed) but no lower, and that is still going to be supersonic.
Regards
Pete
Ps, hodgdon only list a 150gr nos bt sub load, which isn't even subsonic, and by experience, the 150's don't stabilise, where the 175smk will (in a 1-11"twist)