Operating system: Ubuntu
Short description of error
Select then deselect is not same as deselect then select
Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).
In Edit mode ,
Group vertex group select(orange) is a strip of 1 raw width. (faces mode)
But when All faces selected, Group > Deselect ... deselection(purple) is not same as Group : it 3 raws large, instead of 1.