It could also be because as I said earlier their coding is so bad, they don't know what they have.
A distinct possibility. As I mentioned, perhaps their attempted proof of reserves (which doesn't actually prove anything) has exposed a hole in their finances, and now they are scrambling to figure out if they are actually solvent or not.
Of course, 0.0005 for a withdrawal to SegWit btc address seems very expensive
Let's just point out again that such a ridiculous withdrawal fee is completely artificial; an arbitrary number picked by Binance which could be 99% lower and still cover the network fees.
The only thing that is going to be popular nowadays among small traders not to withdraw their bitcoin from binance is the expensive withdrawal fees.
Which is exactly the point of these fees. They don't want everyone withdrawing because they can make more money if you don't, and they might run in to a liquidity crisis if you do. So set astronomically high fees and know that the majority will just leave their coins on the platform.