As I've only ever had to do a N/S seal I didn't know about that until a few years ago when I read they were different on our forum - Maybe one of your posts PB? Makes a lot of sense though doesn't it?
Good point too about the little tensioning spring, without it a leak is almost guaranteed and you can damage or displace it during fitting. I'm a bit obsessive with procurement of seals, mostly because there's often quite a bit of work involved in gaining access to change them and I don't want to have to do it twice.
One of my most useful local contacts are these people:
https://forth-engineering.com/ who go well above and beyond to try to help. They've obtained obscure bearings and seals for things like my old horticultural machines and even managed to get a primary unit shaft bearing for a DAF variomatic unit I rebuilt maybe 30 years ago which DAF said could not be supplied - recon unit only. They know all about grades of same size bearings and will sometimes suggest a bearing of superior quality to the original fitment. They have no references to the automotive machinery the bearing fits so you either have to take the old part in with you or provide very accurate dimensions. The seals and bearings always come in their own nice little boxes. I've also benefited from the bewildering range of pneumatic fittings they stock. Very good people to know!
I find that between them and these people:
https://georgebrown.co.uk/ I can usually tackle anything I'm trying to do.