Scotland's higher "Other receipts - Gross operating surplus" per head are mainly due to accounting adjustments relating to Scotland's higher capital expenditure per head
This one is very much for the geeks.
Taking 2024/25 as an example: The total figure for "Other receipts - gross operating surplus" was £8.9 billion.
Per GERS Table A.9, £6.1 billion (68%) of that figure relates to capital consumption adjustments (mirrored by identical accounting adjustments on the expenditure side). Given that we know accounting adjustments on the revenue side are (in aggregate) >£300 larger per head than the UK average, it seems reasonable to assume that these revenue accounting adjustments are likely to explain the majority of this per head difference on the revenue side.
The operating surplus (profit) of public corporations like Scottish Water are also included. Because Scottish Water is a publicly owned corporation whereas equivalent water companies in England and Wales are private sector, we would expect Scotland to have a higher Gross operating surplus per head. On the expenditure side, Scottish water fairly consistently accounts for about £100 per head of public spending - so it doesn't seem unreasonable to assume that the gross operating surplus will be of a similar scale.
That logic reconciles quite nicely: of the ~£400 per head higher spending for Scotland in this category, roughly £100 can be attributed to public ownership of Scottish water and £300 attributed to like-for-like capital expenditure adjustments. This makes sense, because we know Scottish capital expenditure per head (in 2023/24) was £325 higher than the UK average and this adjustment mirrors an identical adjustment on the expenditure side.