Here is what's confirmed. Bech is off the shelf in the sense that his practice window is now open. He is still on injured reserve and does not count against the 53-man roster yet. Under league rules, Las Vegas has 21 days from the start of that window to activate him or he stays on IR for the rest of the season.
Bech broke his forearm in the Week 3 win over the Saints. Before the injury, the second-year receiver had five catches for 48 yards and a touchdown. That is a small sample, and nobody has said yet how the Raiders plan to work him back into the rotation or how quickly.
What isn't settled is a game date. Kubiak's comments covered practice, not a return to the lineup. A player who opens his window can be activated within days or can use most of the three weeks, depending on how the arm holds up in contact work.
For RSO owners, this is a stash decision more than a start decision. Bech's early production doesn't make him a weekly lineup piece, and a forearm fracture can take time to feel right when catching in traffic. If he's sitting on your IR slot, there is no reason to cut him now. If you need the roster spot for a player who can help this week, he is a reasonable drop in shallow leagues.
In deeper dynasty formats, a second-year receiver on a cheap contract is worth holding through the window to see what role he gets. Don't trade for him on the news alone, and don't spend a meaningful free-agent bid if someone cut him earlier.