I'm just curious what you are basing this off?
As far as I know nothing has been reported as to how he is performing.
For all we know Isabella has been terrible, and Byrd is our best bet as a deep threat.
Because draftees have a better chance of sticking than some undrafted guy who came from Carolina, of all places?
We're not cutting ties with Isabella unless he's historically bad, same goes for Butler, and Keesean Johnson has a better chance than most.
The alternative pathway for Byrd to make the roster is pretty slim. Teams only hold onto a limited amount of guys, and White/Cooper/Sherfield/Williams are competing with him and others for one, maybe two spots.
Before the draft, there were three more positions wide open. The only roster guarantees were Fitz and Kirk.