I don't know how the accounting works for short selling with collateral:
For example if a stock is \$10 a share and turn out to be $15 a share a week later.
At time 0, you borrow and sell 10 shares and get total proceeds $100
If collateral requirement is 50%: you have to keep $50 in the bank, and any potential losses are deducted from there first.
A week later, your position is worth 10 * $15 = $150. If you close, you have net loss \$100 + -\$150 = -$50
Basically wipe out your collateral account entirely, \$50-$50=0
So you still take home $50 which you got from the original sale but weren't required to put into the collateral account.
Doesn't this show you still take home positive amount of money, where as if there was no collateral accounting: very clearly you sold for \$100 and bought for $150, so your loss is very clear.
For shorting with collateral it appears you still have $50... very confused.