Sounds like a move to cut off the retails traders. I hope the 100 contracts minimum won't turn into 1000 and the 10K. I seriously wonder how someone trading for example 1 contract has the power to manipulate the market than those chaps trading 100K contracts at ago.
In fact, this step was very sensible and helped to solve some problems with opening orders. Due to the high price of bitcoin, large slippages began to occur on the platform. That is, you could place a buy order, for example, a limit order at $58 000, but for some reason your order was triggered at $58 015, sometimes slippage reached $35. I saw this when the price was above $62 000.
The problem lay in the fact that the calculations were made in Xbt (this is how Satoshi is denoted on Bitmex). But sometimes slippage worked in the opposite direction, that is, you went short at $58 000, and the order was triggered at a different level, at $58 015. You have opened a position and is already in a small plus, although the market is still at the level at which your order triggered. High-frequency micro-scalpers began to take advantage of this gap in the settlement system and, with the help of bots, began to make a huge number of transactions with such errors. It turned out that they entered deals and immediately exited, because to earn money they had to catch just such a difference in calculations.
Therefore, Bitmex solved this problem:
BitMEX Eliminates Risk-Free Vulnerability for High Frequency Traders
"As the representative of BitMEX explained at the time, the dollar amount is only a displayed value. In fact, the BitMEX engine calculates all orders in bitcoins or, if we are talking about smaller values, in satoshi, rounding the amounts to eight decimal places. with a strike price of $55,509.5 is equivalent to 0.00001801493 XBT, and with a strike price of $55,524.5 - 0.00001801006 XBT.But for the BitMEX engine after rounding, this is the same order for 0.00001801 XBT.
The discrepancy may seem insignificant to the average trader, but it is huge for high frequency algorithms that conduct many trades with small profits. To take advantage, the algorithms placed buy orders at the upper end of the range. Thus, they received a margin for lowering the price in dollars, while the BitMEX engine, which calculates in satoshi, would consider that the price did not change. If the rate really started to fall, it was enough to close the deal. If the price went up, BitMEX saw its change in satoshi and credited the corresponding profit. The same is true for short positions using the lower end of the range. "