Wa alaikum assalam Sardar,
The argument was made in support for the need for justice and the Quran's instruction that one is entitled to their principal back (2:279). If one bag of sugar was lent, then the lender has the right to receive one bag of sugar in return. If one camel was given, then the lender is entitled to receive a camel back. If a car was given, then the lender is entitled to receive the same / similar car back.
However, if someone lent $1000 to someone and 30 years later gives the same $1000 back, then the lender would arguably be at a detriment as the currency is not likely to hold the same 'value / purchasing power' that it did 30 years ago.
Therefore, the argument was made that this 'offset' should be potentially considered carefully as compensatory when dealing with a depreciating commodity such as money so that the lender is not placed at a detriment.
In my humble view, I think it is fair argument that any inflation factor is carefully considered when agreeing a loan so that the lender is not placed at any detriment.
However, of course, if the currency for some reason becomes stronger, then the debtor should be able to benefit by paying less amount back in accordance to the 'value / purchasing power' of the currency.
I hope that helps, God willing,
Joseph