Savescumming in XCOM 2
The premise of your question is incorrect.
In XCOM: EU, savescumming was possible so long as you didn't move, as the seed was generated upon squad movement, and thus it was possible to reload saves over and over to get the desired outcome.
This is false. The seed is generated at the start of the battle - it has nothing to do with whether or not you've moved. Doing the same actions in the same order would always cause the same outcomes, so the method of save-scumming you mention would not have worked.
However, it is still possible to save-scum in XCOM:EU by taking different actions. For example, if unit A misses their shot, reload, have unit B do something, then try the shot again with unit A. This method of save-scumming still works in XCOM 2.
For more info, see the Random vs Seed article on the XCOM:EU wiki.
It's also worth mentioning that XCOM:EW added a "second wave" option called Save Scum, which generated the seed on every reload. Using this option, if a unit misses a shot you can simply reload and try again.
In XCOM 2, there are two mods that do the same thing. One works automatically, but is written in a way that makes it incompatible with a lot of other mods; the other restores compatibility at the cost of having to click a button.
I have noticed that the seed that gets saved in a save game is different than the one you had the first time. Here's what happened to me:
- Beginning of turn, specialist successfully hacks a tower, giving the entire squad re-stealth (iirc 54% chance)
- Moved another soldier. During the move, the game froze up to where I had to ctrl-alt-delete.
- Reload from auto-save
- Specialist can no longer successfully hack the tower. I spent over an hour trying different combinations of move this soldier here, move that solder there, going into the next turn even, specialist could NOT hack the tower again to save her life. After dozens of re-loads, I finally gave up and proceeded with the mission without the tower bonus.