You could, but the reason that companies ask for CLAs is to free themselves by that restriction.

If Minio just wanted to use the changes under AGPL, the contributor could just license them under AGPL, no CLA needed.

There are several companies I've seen that use a CLA primarily to sell AGPL exceptions so they can actually fund development, Element for example [1]. Some even word the CLA to require them to keep contributions available under an OSI-approved license.

I'm a fan of that model. IIt allows for a path to funding, a legal framework to keep contributed code open, and also allows them license agility to more permissive license ass needed. I've started using that for my own larger projects too.

https://element.io/blog/synapse-now-lives-at-github-com-elem...

	▲	Macha an hour ago \| parent [-]
		Being able to sell AGPL exemptions is freeing themselves from the obligations of the AGPL. Fundamentally Element’s structure is the same as Minio’s in the lack of guarantee to external contributors that their changes won’t be incorporated into a closed source fork. So elements use of the CLA is standard rather than novel