Flexitarian is a more accurate description of your diet.
If someone is vegan for a year then eats meat the next, do we retroactively revoke their year 1 veganism?
If I am vegan for January and then in February eat meat, am I retroactively not a vegan for January?
It sounds like this person is a vegan at least six days a week. I don’t see how Saturday erases Friday any more than 2023 would erase 2022. And I don’t begrudge them becoming vegan again on Sunday. Who would that benefit? Being vegan 6 days a week is way more vegan than most people.
Like many labels I think it comes down to intent more than timeframe.
If you go vegan and then a day/month/year/decade later you change your mind and decide it's not working then you were vegan during that time and are no longer vegan.
But if you take a hiatus from consuming animal products with intent to go back to eating meat in a few hours/weeks/months then I wouldn't say you were a vegan during that time. If I happen to go a few days between consuming animal products that doesn't make me a vegan during those days.
But nobody has a right to harass me, just because they seen me eating meet outside of my social circle!
If someone tells me they're a vegan, but they eat meat every single week, I would have to put less stock in everything they later tell me, including complaints about being 'harassed'.