Sorry niko. I just added 1 sp to Nunez. His new calculated average quality is 179.53, but his displayed average quality is still 179. Your theory doesn't work.
Nunez
Average quality as calculated = 179.53 (7 sp to 180, expected to round up)
Average quality as shown by T11 = 179
Note: Player has no SA, no multiple position, nor training progress on these
Attachment 62782
EDIT
niko, please just ignore of the first captures for my player Nunez which indicate its attributes before signing. Average qualities of all 3 categories are incorrect. They are just corrected after signing.
As a result, so far I have no evidence to prove that your theory is wrong.