The kill counter for the above abilities/units is bugged.

You can see an example in my screenshots below.

This Ranger squad has 1 kill.

They grenade a squad of Pioneers.



The pioneer squad is wiped, but the Rangers still only have one kill.

This is also an issue with mortars, the US pack howitzer, the Sherman Whizzbang and the 105mm howitzer. I have had a Whizzbang wipe 3 squads of enemies with only 1 recorded infantry kill.

I believe this issue is not unique to the US faction but all factions and their equivalent units within the game, with the possible exception of the Nebelwerfer which appears to track kills caused by burn damage (but perhaps not initial impact damage).

NOTE: the bug reporting advice for these forums directs to a Sega reporting form, when COH3/Relic have not been owned by Sega for some time now. Using the form results in the following response -

Thanks for letting us know about the bug you encountered in Company of Heroes 3. We understand how frustrating it can be when something disrupts your gameplay.

While we track bugs and feedback here at SEGA Support, the developers are most active on the official forums:
https://community.companyofheroes.com/coh-franchise-home/company-of-heroes-3/forums.

Submitting your report there gives you the best chance of it reaching the developers directly. They actively monitor the forums and will be able to investigate your issue.

Best regards,

Vincent
SEGA Support

There should really be a bug reporting channel on these forums to ensure proper reporting and avoid this feedback loop.