FYI Nullist Penals rarely beat a Grenadier in 1v1 up front fight as there so damn fragile. This isn't even factoring in the 50% cost increase in comparison.
Please show a replay or video of this happening. I know old replays were broken by the patch but the scenario you stated isn't really possible without other factors (veterancy, upgrades, lower starting hp, cover, mistakes made by the player).
If it is so common as you state then it shouldn't be hard to recreate.
The effective HP between the two squads is the same and the Penal squad deals more than twice the DPS of the Grenadier squad. Even when taking into account that the first Penal soldier might die before the first Grenadier, this just sounds like BS.
Other than that, the thing about dodging grenades and Satchel Charges in this game is that in online play the command latency is horrible. For many commands this is simply compensated by some animations but for grenades, satches it isn't really.
I think cancelling grenade and satchel throws would actually need to be made less responsive (not allowed to cancel it beyond a certain point) to allow for the whole timer to be displayed properly to both players.
Just throw a satchel in a (local) game vs. the computer and you'll see the timer run down properly.