Ukraine was not applying to or joining NATO. It is completely Russian fan fiction.
They were making reforms to perhaps eventually be eligible to start using the Euro.
So even if the expert you're appealing to is completely correct, it does not match the reality of events.
Euro is out of question. Always was.
In January 2022 th Ukraine didn't had granted even EU candidate status...nor had been provided roadmap or invited to apply for NATO membership nor had active application.
About EUR adoption it is even more difficult than to be full EU member.... Ukr didn't had met criteria even to get

as candidate.
Albania is EU candidate 10 years....in order to get what stuff candidate status means in real life.
Basically candidate status isn't binding contract. You get flowcharts and reccomendations what to do before apply .
.If you don't do...0 sanctions or fines etc...
If you do, then get next flowcharts... approx like this.
This isn't loans or grants with clauses etc...
EUR adoption mainly is ECB decision if country - full member meets actual criteria...
I even a bit scared that they reduced demands BTW.
I might want to see how Ukr might had met early 2000 ies criteria:
State treasury warranted public debt 40% or lesser, reccomended yearly budget deficite
2% ...and inflation % and other things.
Ukr there in 2021 th was not even close to this...