I think the Mongols should start with 7 villagers (maybe even 8), by the time they place and unpack their TC they are already behind on villagers then other civs. If you are playing the Mongols aggressively and are making forward towers then they are 2 settlers behind so if the early aggression does not pay off then they will find it very hard to catch up on eco (could even be game over for them).
What are your thoughts
They are starting with a free ger, that balances the scales.
That is also valid for other civs.
I agree, it feels awkward to watch the TC moving slowly to its position. I see why u are feeling, you are missing out at the start of the game.
But they also have strong benefits during that time, that compensate for it.
If u build your ovoo, it counts for 2 villagers on stone.
Not saying it is super balanced and if Mongol should need a buff during that time, I could see the ovoo getting buffed again, which is also contributing to your eco.
Would you prefer the TC to be already unpacked? To avoid the extra idle time?
If the answer is no, then moving the TC is a bigger bonus overall than it is a nerf for you.
And you get to place your TC to best possible location, while other civs need to build gathering buildings etc and are more vulnerable to early raids
Here is an example of being a settler behind, lets say a Mongols villager can gather 37.00 gold a min (with no upgrades https://www.aoe4-production-calculator.com/).
So in 10 minutes if that settler was put on to gold at the start of the game then it could collect around 370 gold. So the question is is choosing your starting position and starting with a 100 wood ger worth more than 370 gold extra by the 10 min mark.
So other civs only need to spend 50 wood on camps, so it is really -50 wood with a TC unpacked start (will have an extra villager) and could have 370 gold by 10 mins vs choosing your TC start and having a Ger +50 wood (This stats changes with different civs bonus).
I think if the Mongols are unable to kill an enemy villager within 10 mins then the advantage of choosing their TC location has not been worth it and they are just behind.
Watching pro games it seems even they have a hard time trying to get an advantage with the Mongols start and being a villager behind.
Still think the Mongols need to start with an extra villager.
This would be a big buff 
Did u ever try a different BO, with double production of villagers early on? Curious about ur feedback.
I think the devs wanted the ovoo beeing used to compensate for it. It really shines military-wise, double production of units is strong, but to me, it seems the eco approach isn’t.
I think the devs intended it to be used in other ways early on also.
The TC fire change, made it also harder for mongols to apply pressure when they are strong.
On the pup patch the food, wood and mining techs got reduced, mongols will benefit the most from it, when you get the upgraded version with stone. On paper an economic BO with mongols does not seem that strong right now.
In theory, they could be very flexible early on thanks to the ovoo, with a lot of different BOs.
It would be nice if Mongols get the other options balanced out, maybe to reduce the double production of villagers slightly (mb 125 instead of 150). So they can also go for the eco approach and keep up with other civs