It's def. not a non-issue. As you write yourself there some requirements to get there and in general you should do a migration to the GmbH after the end/before the beginning of a business year and not in-between. Just this restriction is a big bummer and paired with the other requirements creates some headache. So, you can't go to the notary and just opt to the GmbH, no you have to consult your tax consultant, find the right time, probably wait some months and prepare the switch properly.
> others seem just wrong.
Are you so kind and tell us which you think are wrong?
In fact the whole UG thing is setup towards this exact goal, conversion to a full GmbH (you even have to sideline profits to accomplish that).
There are indeed some valid things in that comment, others seem just wrong.