I used to use them. They are quick and don't break the treatment seal as you say. Only stopped as i got better at mortising and it was a cost I couldn't easily pass on to the customer as the competition were just notching with a chainsaw, so no added cost.
Easy to use, just cut angle on stay and hammer on, only downside is there isn't much hold against rotation but easily reduced if off setting wire and footing strainer.
The importer sold out but Moncaster products (i think) have taken it on had a shipment in.
Their good to use on a temporary fences, no damage to strainer and easy to remove.