What made dinstall think this was a NMU?

[Richard A Nelson <cowboy@vnet.ibm.com>]

Just got the following from the automagicall dinstall process:
   From: Richard A Nelson <cowboy@debian.org>
   To: control@bugs.debian.org
   Subject: Fixed in NMU sendmail 8.9.3-6
   ....

What made it think this was a NMU, was it because I did the dupload
from work, instead of master/va?  Or is it an indication that my
PGP key is out of whack, or because I used PGP instead of GPG?

Thanks,
-- 
Rick Nelson
Trying hard to return to a quasi-normal life