Teams are free to add players all the way up until the first few weeks of school (typically 15 to 30 days) and as long as they are a) eligible to complete at the NCAA level b) team has roster space c) scholarships are available (if given a scholarship) d) if a transfer that his prior school submitted his name into the portal and got clearance.
The portal close date has more to do with administrative elements for setting rosters for the next academic school year. As far as I understand, the only barrier after the May date is how the authorization process occurs for portal entry. Most schools have rubber stamped this since the 1 free transfer rule was implemented two years ago. Players know that it is sort of with cause (why you'd leave after May) and there might be a hold up for clearance.
As far as I know and have read that as long as the player has a free transfer there isn't anything stopping them to transfer after May 1, it gets a bit more conditional (roster limits, scholarship availability, etc) and complicated. My understanding after May 1 schools cannot add players without having space on their roster and removal of the one year funding cannot be undone by the school (pulling the scholarship) unless there is a non-academic progress issue.
So I think from what I gather DCH was free to transfer and likely won't have to sit. Next year.