It’s an excellent idea. I’ve read, and it makes sense, that any radioactive waste that leaks out would be diluted to the point of being not even negligible.
Plus, the ooze apparently has some kind of electrostatic attraction that makes it permanently seal it in, so even in the event there WAS a leak from a cask, it would be entombed as surely as if it were buried deep underground.
Sounds a lot better than storing it in rusting 55 gallon drums inside a chain link enclosure...