That is only accurate if they can provide a meaningful defense against expected attacks otherwise all you are doing is creating a single central target. Unfortunately, the cloud providers can not mount even a token defense against an attacker funding an attack at the $100M level, so I see no reason to assume they can defend against credible threats to a single Fortune 500 company given that they can not even stop an attack with such a meager amount of resources allocated to it relative to the size of a Fortune 500 company. That is not to say that the teams in a Fortune 500 company are any better, merely that everybody is completely inadequate.
By consolidating targets when you can not even reach the level to protect a single one you are making the situation worse, not better by consolidating. For it to make any real amount of sense they would first need to demonstrate an ability to prevent attacks at least in the correct order of magnitude and then demonstrate that they can scale up without creating correlated risk. Only then does it make any sense to actually centralize on a single solution, let alone a single provider.
By consolidating targets when you can not even reach the level to protect a single one you are making the situation worse, not better by consolidating. For it to make any real amount of sense they would first need to demonstrate an ability to prevent attacks at least in the correct order of magnitude and then demonstrate that they can scale up without creating correlated risk. Only then does it make any sense to actually centralize on a single solution, let alone a single provider.