You don't need to limit yourself to Manglik-only matches.
Yes Mars in 12th with Moon opposition technically qualifies as Manglik by classical rules. Not disputing that. But the way this dosha actually plays out depends on more than just position.
Mars here is debilitated in Cancer. That changes things. This isn't the aggressive 1st or 7th house Mars that creates real friction in married life. Debilitated Mars turns inward. More likely to show up as frustration, stress, suppressed anger rather than explosive conflict. Still something to watch, but the texture is different.
The idea that Manglik must marry Manglik is repeated so often that people treat it like a law. It's not. It's one way to balance the energy. But I've seen non-Manglik partners with strong 7th lord or well placed Venus work out fine. The chart has to be seen as a whole.
What I'd pay more attention to honestly is Moon compatibility between the two charts. Navamsa health. Venus placement. 7th lord dignity. These tell you more about how a marriage will actually function day to day than a single Manglik label.
The timing point already raised is valid too. If the stress periods activate later, that's information about when to be careful. Not a reason to reject every non-Manglik prospect now.
Check the dosha properly when you're actually comparing two charts. That's when it matters. Treating it as a standalone filter before you even have a match to evaluate is how people eliminate good options for no reason.