Not likely. There are plenty of metamorphic rocks far older than 800 million years. Metamorphic rock is almost always in part formed as a result of deep burial during the mountain building process (also high temps and pressure). Mountain building, outside of volcanoes, is a direct result of plate collision, via the plate tectonics process. Some metamorphic on earth are radio-metrically dated as far back as 4 billion years.
...actually, most volcanoes too are the result of plate collision/plate tectonics. But that’s really another subject.
Also metamorphic rocks can have their mineralogical ‘clocks’ ‘reset’ by later periods of plate tectonic activity/mountain building, and so can appear to be younger than they actually are. However, as far as I know, none can be made to appear older than they actually are. And so one with a date of, say, 3.2 billion years, is at least that old. Make sense?