This is a strong speculation although there is some sense in it I still don't think it is possible. Even El Salvador should know that Bitcoin and the crypto-currency market is very volatile and using borrowed funds to buy Bitcoin has its setbacks.
El Salvador might be a small country but I don't think they should have any problem getting one Bitcoin a day looking at the current price of Bitcoin. I believe they have serious Interest in Bitcoin and they can easily channel the country funds from else where into purchasing Bitcoin.
So far, there is no concrete evidence that El Salvador is using borrowed money to buy bitcoin. It's all speculation, because if there was evidence, the IMF would immediately stop the loan because they were in serious violation of the loan agreement.
El Salvador will have enough money to buy bitcoin with a 1 bitcoin per day strategy because this is not a large amount for a government. But the problem is that the IMF sets an additional condition that Public sector funds cannot be used to buy bitcoin. If El Salvador doesn't use Public sector funds, what money does it use to buy?