I think that you might be conflating retail shorting with institutional shorting.
Retail is subject to a Reg T amount of 150% of the value of the position at the time the short is created but since the full value of the credit shorted position is included, it's effectively 50% margin. When short, we pay a borrow fee. Some brokers share that fee with the lender. At my broker, if the current fee rate is 16% and the current rebate rate is -15%, the borrower would pay 16% and the lender would receive 15% with the broker taking 1%.
The shorter pays a daily borrow rate which fluctuates and accrues daily. It would show up as a daily debit on Tuesday through Friday with a three day debit occurring on Monday (Friday plus the weekend). So if you short a stock and buy to cover a week later, you would pay seven days of borrow fee, each day at the respective daily rate.
Institutional borrowers (hedge funds, fund sponsors, etc.) borrow from a counter party and post a cash collateral which protects the lender from default. The amount required is usually about 102% to 105% of the value of the security that was borrowed security. The position is marked-to-market and the amount of the loan can fluctuate, requiring more collateral or a refund.
The Investopedia article that you referred to has to do with the complexities of this institutional borrowing not retail shorting which I described above.