Sorta.

Since a couple of years ago, new EU members are obligated to eventually become Euro members, and non-EU members need the agreement of the rest of the EU to have any say in how the Euro is managed (sure, non-EU countries can do the equivallent of dollarization with the Euro and just use it as currency or have a pegged currency, but that means no ability at all to participate in managing the currency which is what really matters for Germany in order to get all those sweet benefits of a currency managed taking in account weaker Economies) and there is only a handfull of small countries with such agreements.

By leaving the EU, Germany would immediatelly loose the right to have any say on things like how the Euro is managed and would have to negotiate any such things in the Exit Agreement.

So your "point" sounds a lot like the fantasism I heard in Britain from the Leave campaign: all about "we can still have this and that" whilst the reality was that ex-members are not entitled to an a la carte choice of all the things they want and have to negotiate it with the rest of the EU and since what comes out of that negotiation requires unanimous approval, they're not going to get all that they want and what they do manage to get will cost them.