I've been noticing sometimes in the last few patches, including the current one, that sometimes Grenadiers rifle grenade will shoot before it's animation, delaying all detection to significantly less than 1/2 a second. I don't know why it occurs or if it's controllable, but here is some proof and documentation.
I'm including a replay, which you can see the event at the Church, between a Grenadier and Airborne squad. The rg is launched and right after the midpoint of the arch, the grenadier begins the animation, at time 19:17. Here are some photos if you don't want to download the replay.
This first screenshot shows the grenade just before it's midpoint. I captured it so the projectile could be seen against the contrasting snow covered roof behind it. You can clearly see the grenadier has not done the animation.
Here you can see the grenadier start the animation
You can now see the grenade is just about to impact and the grenadier squad is still in the late animation. I've circled the projectile, it's very hard to see, but it leaves a tail which you may be able to see (it seems my red circles only show up on photobuckets site, so click picture if you can't see the grenade).
Here is the impact and the grenadier finishes the animation at the time of impact.