The biggest factor for me in picking a WR if there at 9 is the depth and succession planning. If Odunze or Nabors is the pick, the 4, 5, 6 receivers are still Tyler Scott, Velus Jones, and Dante Pettis. An injury to Allen or Moore force that group into action if no NFL ready player is taken. Yes they could still sign someone, but the pick at 9 should be better than what's left out there.
The succession planning component you mentioned. Having Odunze in place for his year two with Allen's target share is a great prospect and avoids starving Caleb of weapons.
I have to wonder if the team isn't going to extend Moore. With the prices of players continuing to rise the smart play seems to be to get the extension done sooner rather than later to buy lower. Even if you're paying top of market prices in a couple years it looks like a good deal. Not sure if Moore would want to extend now or not.