I think you are mixing the segwit block increased with op_return relay policy. The segwit was years ago, the op_return relay policy increased the data carrier size from 83 bytes to 100kb when they released the Bitcoincore v30.0 which was last year and it's not a standard, it's a policy rule but you can increase it to any amount within the range of 0- 100kb. You can even disable it if you want.
As far as I know there is no consensus limit restrictions for OP Return other than the overall block weight limits which is the only reason I stated the 4MB for Segwit and 1MB for non Segwit as the block weight limits.
The bitcoin core v30.0 policy is within the standardness rule which was earlier proposed to remove the earlier 83kb limit and it’s the rule that has it at currently 100kb AFAIK but no consensus limit restrictions.