I'm struggling to piece together all the data you have put forward here bud so I apologise if I have misread/misunderstood and end up not answering your question very well
With the SU, because the divisions are under a corp and the SU are under northern front HQ, meaning they have to go up the chain of command to coordinate together you will have a diminished chance of them activating so I imagine in your circumstance only a couple or so would likely end up activating
As an added tidbit for the uses of fort construction certain types of divisions have multiplied values of construction when building level 1 forts under certain circumstances
For example an infantry, cav and mountain divisions building in your own ZOC that has not been recently flipped, without any enemies in an adjacent hex, in light terrain will have 3 times the construction value when building a level 1 fort, meaning if you have a division with 20 construction value you can get a level 1 fort in 1 turn
Tanks in the same circumstance get twice the labeled construction from what I can tell
It's really quite simple and perhaps I've made it more confusing than it needs to be. I started the game human on human and on GHC Turn 1 I did nothing other than hit end turn. On SHC 1, I moved like a grand total of 4 units. I put the HQ in range, I put the 3 units I've noted in a clear hex, and I built a ton of extra construction units in the Front HQ. So just put a few units into a clear hex, made sure that the Command chain was good, built some SU's, and hit End Turn. Then I did nothing other than hitting end turn for both sides until I wrote this post at Turn 5 start.
It's inconceivable to me that 50+ total Constr Value (2 Inf Divisions and 1 Tank Div) can't build a Fort Lvl 1 with all of that construction support in that amount of time. As you point out, without any Fort level they should be getting BONUSES to build the Fort...but nothing. All of them MAX TOE including support. The MOT Unit next to them built to Fort 1. It's crazy man.
I just ran through another turn (had company over which pulled me away) and FINALLY when i opened the start of SHC Turn 6, there was a level 1 Fort.
Don't take my word for it, put some units in that same hex (1 hex SE of Pskov) and see for yourself....
Side Note: Like i said, i've basically done nothing other than hit "end turn" for both sides since intially moving those three units on Turn 1 and the GHC have suffered 81554 Casualties including 16k+ killed and over a quarter million for the SHC including 25k killed and not a shot has been fired. ;-)
< Message edited by MattFL -- 3/21/2019 6:47:11 AM >