We simply don't have all the facts to judge that. Shanks could simply have had some secret intel that something is going to happen to Alabasta and he concluded that this is the best time for BB to make his big move and sought the WG help among many other such scenarios.
I mean, we do lol. Nothing "happened" to Alabasta until Cobra decided to ask them questions. There is dialogue that talks about this in 908. It wasn't "planned" before then.
But sure, you can think what you want lol. I'm just pointing out that it does NOT make narrative sense to hide the subjects name when we already know they hate each other. Not when Blackbeard hasn't done shit post timeskip.
Remember the Shanks/Whitebeard conversation. It started because Thatch was killed and Ace went after BB. There was a reason for the conversation.
Right now, there was zero reason in the story for Shanks to talk about Blackbeard. Nothing happened with the character until 956.
The event at the Reverie was not pre-planned. The Gorosei literally mention in 1037 that they've been dealing with that headache, as if something got out that wasn't supposed to happen in the first place. Information leaked out and its cause huge problems around the world