I'll give a bit of context.
The bill is not targeting all cryptocurrency / foreign assets holdings, but those which were (illegally) undeclared from subjects who have the obligation to declare their funds. In Argentina (like in many other countries which have some kind of wealth tax), if you have any kind of property which exceeds certain values, then you have to declare it and pay a wealth tax for it (called
Impuesto a los Bienes Personales). The threshold is
currently at 6 million Argentine Pesos (approximately 50.000 US dollars, depending on the exchange rate you apply, there are big differences between "official" and "unofficial" rates), but a house you're really using is not included (at least if it's not worth more than 30 million, or ~200.000 US dollars).
The new bill is a way to "legalize" formerly undeclared/evaded funds paying an extra tax on it. It is, however, only applied for funds exceeding $500.000 USD. Of course you can try to continue to not declare your wealth but the longer you wait the higher the tax will become, and when they discover you still hiding something, then a fine (or even prison, in extreme cases) is added.
In fact, the bill is criticized by the opposition because it gives tax evaders an easier, less harmful way to "legalize" their funds ...