No. I definitely seen people who created multitude of misleading bug reports, flood of stupid feature requests. I personally did a bit of both.
There are people who do both repetitively, fill issue reports without filling requested fields. Or open issue again when their previous report was closed.
I got once bug report where someone was ranting that app is breaking data. Turned out (after wasting my time on investigating it) that user broke data on their own with different software, through its misuse.
There were PRs adding backdoors. This is not a valuable contribution.
There were PRs done to foment useless harmful political mess.
Some people pretend to be multiple people and argue with themselves in pull requests or issues (using multiple accounts or in more bizarre cases using one). Or try to be listed multiple times as contributor.
Some people try to sneak in some intentionally harmful content one way or another.
Some contributors are NOT valuable. Some should be banned or educated (see https://www.chiark.greenend.org.uk/~sgtatham/bugs.html ).