"objective performance criterias" in a development role is a joke.
In a motivated and well performing team, everyone has a pretty good gut feeling on who's slacking off and pretending to work.
Unless ... the whole team is full of slackers who want to collectively engage in theatrics and perpetuate that there's no such thing as objective performance metrics in order to not be exposed as slackers.
> everyone has a pretty good gut feeling on who's slacking off and pretending to work
I remember one such case where I had a gut feeling, but I didn't undertake any action. Writing to a manager felt like snitching, and I could have been completely wrong (maybe they had valid reasons, unknown to me, to have low productivity), which would cause me embarrassment. I think it often takes a team consensus, sort of validation with somebody else. But such sensitive topics are often communicated subtly, indirectly, with body language or voice intonation. But I won't be writing my colleague on Slack if they share my suspicion...
So they have a senior dev look at the requirements of the task to check maybe the estimations was wrong or the way it was formulated was bad, and also have a look at what that developer in questioned has checked into Git and start asking questions on why the slow process.
You can bullshit the non technical people, but you can't really bullshit your peers/seniors for too long before they realize your underperforming, when they start looking into your work.