I think it was that Michelin wanted to give R5 drivers a better tyre against Pirelli (7mm), as before Michelin for R5 had the same tyre as wrc cars (6.5mm) and were 'loosing' to Pirellis so to say... Just guessing
It`s not just the protrusion that`s different compared to the WRC tire it`s a completely new tire as well though it looks the same..
Think I'll go to bed and just listen to the commentary.
[WRC] FORUM8 Rally Japan 2025