Blockstream does not decide if changes are made to the Bitcoin core, the community of devs does.
Yes, the blockstream controversy is likely just another conspiracy theory. Along the lines of Gavin being a CIA mole, etc. I think it's just that the "community of devs" often disagree and Wladimir doesn't want to dictate the direction.
tbh there's more credibility to the "conspiracy" that Gavin has been compromised by corporate interests than anything related to Blockstream