I gave out all explanations in my post but you could not understand them.
Why many forex brokers offer very high leverage because it is not uncommon that a forex trader holds like 10 or 20 pairs positions and trade 10 pairs at the same time. Each pair does not take much margin but 20 or 30 pairs need very high margin.
It is not that if you have $10000 buying power and each pair need $1000 margin, so you can trade 10 pairs. You still need some room for your positions when the they go down and take more margin. So probably you will need $20000 to hold or trade 10 pairs.
The red text confirms that when you catch an open loss on some positions, you need more money, so more margin. The aim of a margin is to protect the broker against your losses. So the reserve just in case if the positions go down is called MARGIN.
You use it to go under the initial $1,000 margin that you have. So in reality your margin is not $1,000, but more. If you need 20K to hold 10K margin positions, your margin is $2,000 instead of $1,000.
My reaction was on the ES. Were you not speaking about the ES and $5,000 margin?
Without the $500 margin you would not be able to keep all these positions, so you use the $500 margin, you need it. My conclusion is that your real margin is lower than $5,000. Take away the $500 margin and you get in trouble.
I cannot see how the $500 margin can be useful if you don't use it. Useful means good for using. If you don't use it, it is not useful. But if you use it, your pretended margin is fake.