As per this Reddit thread from Nov. 13, 2020: https://www.reddit.com/r/DestinyTheGame/comments/jtpubb/nessus_public_event_glitch/
If you have a bounty that wants 2 public events done, for example, you could do 20 of this public event (normal or heroic, doesn't matter) and it will count as zero.
Meaning this issue has existed since the launch of Beyond Light at a MINIMUM, and is still not fixed. I find it hard to believe it hasn't been posted here before, but I didn't bother looking because CLEARLY it's being ignored anyway if it exists already.
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So they recognized this as a problem for OTHER events and the patch notes say they fixed it for those ones specifically... but not this one. Still. Awesome.