Dollarization is a misnomer for what Milei is trying to do. Dollarization means to replace a countries currency with the US Dollar. This has been done in Panama, Ecuador, El Salvador, etc.
It requires huge USD reserves, because the first thing the Central Bank has to do is buy all the existing currency and pay for it in dollars.
What Milei actually wants is for Argentina to not have a preferential currency, and to allow businesses and customers to choose whether to transact in ARS, or USD or Bitcoin, or whatever - with no penalty applied to any of those choices.
This only requires laws allowing Argentine banks to offer dollar denominated accounts (or whatever other currencies people want to use).