It is, which is why I highly doubt that is what happened. There's a lot of transition going on at the Buffalo plant. I would not be surprised if there are people being hired and fired.
But like the Fremont factory, there may be a few workers pushing for unions but it is unlikely they have made many inroads. Not enough that Tesla would be that worried.
Plus they aren't that stupid to do something blatantly illegal, would think. You get rid of them for other reasons and at least try to make it look like it's not a reprisal.
And I'm kind of doubting this source.