300blk Bullpups + Subsonic ammunition

I have come across information online suggesting that a 16" barreled bullpup paired with subsonic ammunition may result in the round becoming supersonic due to "excessive barrel length."
Considering the compact size of a Bullpup, which is already similar to an SBR, it could potentially be an excellent option for 300blk.
What are your thoughts on this matter?

What difference will the barrel twist make? Ive seen 1:6, 1:7 and now 1:8 twist barrels in these bullpups.


Some Side by side vids with a chrono visible shooting subsonics.

Underwood 225gr ,<- Click for the video

200Gr  SnB <- Click for the video

American Eagle 220gr <- Click for the video

Interesting.
Some 300blk subsonic rounds will still penetrate some soft body armor.