To sum up the testing.
1 day --> first impressions, overall positive vibes
2 day --> It's Lawson so mostly ignored, inconclusive
3 day --> Trying to add/go for performance, then issues arise
I think the phenomenon is very similar to last year and also very similar to what other teams are experiencing.
They can create very impressive numbers in WT and CFD, but the higher they go with performance the more instable it gets. I think at this point all teams could create a a floor with massive downforce, the problem is to bring it to track reliably.
The challenge is to find the best compromise between predictability and peak performance.
I think Newey was great in finding this balance. Now RedBull seems to be going to the data-driven Mercedes mentality, chasing the magic numbers from the CFD. And get very similar results. (Aston, Ferrari etc have been all here as well to various extent)
McLaren seems to be the best now in understanding this. (although even them had slight problems with this, delaying their floor updates toward the end of last season)