They didn't even know Thor was coming. It's not like they'd be like "We just have to stall long enough until Thor comes!". They didn't know he was coming. For most of the battle on earth in Wakanda, Thanos isn't there. If you insert Thanos into that fight earlier because he's not being held up at Titan, you have a determined Thanos with 4 infinity stones. We saw what he can do with the power stone and the reality stone. Thanos is there earlier, so Shuri's progress with Vision is halted earlier. Thanos could even take the mind stone at that point.
Consider also, that 2014 Thanos in Endgame gives them a hell of a run for their money and he doesn't have any stones for a lot of the battle.
Strange would have known, easily. But Thor wasn't coming to Titan, so there was no point in stalling there. If Strange was on earth, with the Avengers, their Endgame would have been to wait for Thor. Even if Thanos got there earlier, that's fine, because he'd just spend the time looking for the stone. It's not like Titan took him a particularly large amount of time, after all. The Avengers 100% could have held out until Thor arrived. ---
"And no I'm not signing your twitter after this type of attitude so don't ask..." - IIINCORRUPTIBLE