3 different papers in 2.5 years with a group? Did they all have to be lead author works? And if so may I ask what is your field?
That kind of requirement would be way too strict for some fields. Flexible graduation guidelines can be abused by bad programs and/or bad PIs, but they also allow flexibility in what you get out of the PhD and when you can leave. I know people that graduated from my program with 0 lead author papers (and <= 2 contributing author papers) because they had already lined up an industry job or a pivot to research in a different field. They'd be in school forever if there were strict authorship requirements.
PS - some PIs, whether intentionally or not, can actually abuse strict requirements more than flexible ones. If you used PI resources to do research, which is often unavoidable in experimental fields, you need their permission to publish. Some PIs have extremely high standards for what journals they will allow their work to be published in. Often students end up with 4th author via a piece of a paper that got published in a journal like Cell, but could've been a stand alone lead author work in a mid tier journal. Nothing wrong with that, arguably it's better from a scientific perspective, but you can see how that might impact student careers.