I think you missed the point there.
There have been unconfirmed rumours on bob is the oil guy regarding Toyota oil manufacturers for many years .I expect everyone knows Toyota don’t make their own.
No opinion has been expressed if it’s good or bad.
The point :-
When the GR is built in Japan it is filled with ilsac gf 6a which is an SP.
When it is serviced in the uk it is filled with ilsac gf5 or SN+ (and some haven’t even had that).
SP specs are better than SN+
Why are we getting a lesser spec than Toyota have written on the oil cap ?
Does it make a difference?
Would the afe extra they are using in UK make the spec for SP and they just haven’t submitted it?
No one knows but the diligent would like answers.
SP has better Lspi protection than SN+ and it is a concern for Toyota as the link shows.
I totally accept many owners do not care but obviously some do. In the link above from Toyota it lists lspi symptoms and a diagnosis flow which it appears from other threads some Toyota dealers can’t follow.