Query store data maintenance background tasks
For the query store to be consuming a lot of IO I would say, by my experience, that there is a lot of change in the data calling methods.

Are you aware of any reporting with new filters?
Any major change is Store Procedures parameters that might cause parameter sniffing
Any other change to an Application that consumes data in the sense of querying with parameter changes?

I'm asking since these situations create new execution plans and those create data in the Query Store, causing the IO.