Sadly, it would appear this issue had been known for a number of years but no progress has been made with the developers. As a HubSpot partner we have clients with sales teams that leave a company/contact as unassigned becasue all sales personnel have the opportunity to work it. In addition we have users who need to email managers and every time I unassign the company contact as soon as one of the salesmen emails them they become the contact owner and the other sales people cannot access the record.
Support sugested this work-a-round which willnot work in any of our use cases but it may work for someone else. Good luck!
“Would you consider at least changing the user permissions from “Owner only” to “team only”. Then you could create 1x placeholder user for each team and assign those contact to the respective place holder user (owner) for that team and the remaining users within the same team still would be able to access the record.”