Currency collapse is extreme inflation; and that goes to the central point - there are a very wide range of numbers between 0% inflation and hyperinflation (20+% numbers).

Government monatisation isn't that much different from any other tax, except for the rather critical fact that nobody knows who is paying it. That makes it the least intellectually honest type of revenue raising, and the most likely to spiral out of control. Bringing it in is a pretty telling indicator that a country is unable to govern itself. It is a terrible idea. But it is unlikely to cause a currency collapse if they print and bail out the pensions. It'll just destroy some wealth.