Eh.. They probably can, but after several games of ironman I've still never seen any of my single-planet protectorates catch up. And I've had dozens of them, because I tend to play as pacifist liberator.
The game ends long before protectorates start catching up.
5. That is the amount of free Research every emprie gets.
95%. That is the reduction in reserach cost price protectorates get in 1.4.1
A tech with a 360 base needed 72 months to finish (likely a bit less, as Skill and Traits from the researchers affect that).
For the protectorate, that cost is cut to 18. 4 months. Thier reserach speed is literally 20 times yours. And not like thier buildup will be stifeled new building tech not becomming avalible.
The thing is, apart from influence I also uplift to gain pops I can colonize planets with. Those protectorates you want to become vassals ASAP.
True. That might be the main reason to have them go to Vassal.
I realy hope there will be a rework of the Vassal States/Pre-FTL interaction. To allow us to get pops from protectorates.