Transaction fees for stablecoins are ironically higher than Bitcoin right now, but lets pretend they do see broader adoption. Stable coins still use the private/public key address system for sending and recieving payments that Bitcoin does and that could be a barrier to Bitcoion adoption that a stablecoin entry point could help solve.

However, I would maintain the opinion that the other aspects you mention in your PS, would cause people to migrate from stablecoins to Bitcoin since the technical barrier is no longer an issue for a stablecoin user.