I think it's more the results of the brain drain I remember talk of during the big poaching campaigns from Red Bull and Aston back in 2021.

The overarching Mercedes design philosophy also doesn't seem suited for ground effect cars, which was a problem during 2022 especially (though they might have changed philosophy since). They used to want to build a very peaky car, and then use their tools and know-how to get the car into that narrow operating window. That doesn't seem like a good approach with these regs, however. Partly because the strict suspension rules that hit Merc hard, and partly because these ground effect cars seem to favour a wider operating window.

It also must be said that something is obviously wrong with their wind tunnel/CFD setup. Maybe it's related to the personnel they've lost, maybe it's something systemic that only made itself known with ground effect cars for one reason or another. But it's now three straight years running where they've had massive correlation issues and had to publicly and repeatedly state "yes well, the car isn't performing and we don't understand why".