I think those DB talgo sets are no longer around?
Indeed not, because DB have stopped all sleeper services, though I think they were withdrawn some years before that.
That said they too may be unworkable for CS. I believe the reason for the issue was that if someone was lying head towards the direction of travel and there was a collision, they would end up with a broken neck/spine (and as they are asleep they don't "see it coming" and protect themselves with their hands, say - basically they're dead or paralysed before they even know about it). If the trains only went one way with no reversals that would be fine with longitudinal couchettes, but because of the reversal at Edinburgh[1] that would be an issue unless you woke everyone up and turned them round, while with the pods it wasn't realistic to have them all facing the same way and turn the stock each time.
Edit: And if you were going to put pods sideways on up one side of the coach, you might as well just put 4-in-a-compartment couchettes in, it'd take no more space, probably less because you could double-stack them. Though something more suitable for single travellers like transverse Japanese-style "capsule hotel" type things might have been worth a go, unless they would cause too much of a rescue issue in the event of a collision.
[1] Is that just the Fort Bill? If so maybe it would be workable as long as they weren't offered on that portion. Though ECML diversions would be an issue.