I'm a scrub and noob (playing only 4v4), but I've started to tech grenades really early in game, after my 2nd or 3rd riflemans. Grenades help a lot when dealing with MGs/garrisoned units.
When playing on an Arranged Team and on certain maps, it can be suitable for 2 Americans to both go Cpt/Stuart, but one player get nades before.
It does delay, but on certain maps it's necessary to be able to fire smoke grenades into houses overlooking fuel/vp/cutoff points.
Port of Hamburg is an example.
Kharkov is an example.
Lienne Forest is an example.
If for some reason you've lost a building early game, can't force enemy infantry out (the ones holding it for the MG), then nades as your first fuel purchase are necessary.