Changelog says:
Urban warfare twin flamer upgrade for Sturmovie doesn't happen automatically. Now it gives the option for Sturmovies to upgrade to the twin flamers for 100 munitions.
Once I got this feat and recruited regular Engineers (with Storm Engineers upgrade done in Arsenal), I found out that they have no more flamer upgrade (neither single, nor dual) - and that there's no flamers in squad by default. But when I recruited Storm Engineers, I saw twin ROKS upgrade as it should be. So it looks like Urban Warfare deletes single ROKS as an upgrade for all Engineers (regular and storm alike) and enables dual ROKS but JUST for Storm Engies.
Offtopic: I know that's 2 flamers, but isn't 100 mun a bit too expensive for infantry weapon upgrade (doctrinal, I might add)? Maybe it's worth lowering cost of duals to 75 mun?