[mst]

Historically they've generally politely ignored community rebuilders and got a trifle enervated by commercial rebuilders - they changed how they handled distributing kernel code (to a fully patched tree rather than a pristine tree and a stack of patches I -think- from memory) in response to Oracle doing a commercial rebuild.

Exactly what the triggering incident was this time they've been very careful not to officially say (which is likely a better option than the optics of getting into a finger pointing war with a smaller target), and I suspect we won't be able to fully judge their motivations unless/until the details leak and/or are inferred by people close enough to the situation to guess correctly.