Simple, Radio Operator II squad doesnt even provide anything unique, its work like the tier 1 counterpart and can call same thing like tier 1 also. Radio operatior II i suggest can call Arti with x1.2 or x1.5 bigger HE shell, and can call 100 kg bomb instead 50 kg bomb
AT squad should be able to build better AT gun than engineer AT gun, it does give something unique. Engineer AT and AT squad AT gun have same AT, its 50mm, im okay if anti tank squad tier 1 only can build 50mm gun but for anti tank squad tier 2 and 3 should be able to build better AT gun like 75mm AT gun.
For now, there is no reason to use both squad beside leveling gun/leveling soldier
The inherent trait is the only difference between any tier of any soldier. Well that and the cost to upgrade their max level
A Rifleman I can use an M1 Garand W/Nade Launcher
An Assaulter I can use a Lanchester
They all have the same perk pools and use the same weapons and fill the same role. The Radio Op I and Radio Op II have different inherent traits is all. Although much like Engie II’s can build MG Nests while Engie I’s can’t, I wouldn’t mind AT Squads having the same difference. A bigger gun for a higher tier squad would be nice. Especially since some of them lack effectiveness against certain tanks. Plus I’d never turn down a chance to use the 3” cannon