I guess @murchandamus might chime in at some point, but to quote him a bit from that link:
However, if the timestamps are accurate, it is possible that Foundry found both of those blocks just after the competing blocks were found, before they had learned about the competing blocks, but after their block would have propagated widely on the network.
It could perhaps even be the case that the block was found by a pool participant even after Foundry saw the Antpool block, but before they had updated all the jobs. It would still make sense and not be malicious for a pool to mine on their own block when they have one.
As I mentioned above, Bitcoin Core nodes will request and store blocks in competing chaintips with the same PoW as their best chaintip, but they will not announce those blocks to their own peers. Even if Foundry had announced it after having found it, the block could have not made it beyond the Foundry nodes’ peers if they all had seen the competing block before it, or it would have possible made it another hope from a few peers before getting blackholed.
Thanks for these details. So, it’s not a huge leap to say that it was mostly a coincidence that some nodes didn’t see Foundry’s blocks until after the reorganization?
I think that it is plausible, yeah. And if we’re honest, Bitcoiners tend to entertain conspiracy theories perhaps a little to enthusiastically.