They may be planning to pay fiat users BTC, ETH etc on 25th July rate which is a popular demand of fiat users. Maybe that's why the percentage is same.
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I wish this were the case & I think that this would be fair because most fiat holders were only holding fiat by chance and would probably have been in coin if the timing were slightly different.
However I think they propose to set the conversion date once the exchange is up.

"With a balance of 1000 USD, after conversion you will receive 55% in BTC, LTC, ETH (at exchange rate on the day of conversion) and 450 USDET. By this principle all koins and fiates will be converted. "