It is correct that EU member states are not 100% sovereign, they need to implement EU law.
It's also correct that the term "sovereign" is used incorrectly in this headline; I think what they meant to say is "independence".
> [...] it seems that commenters do not use any as soon as the EU is mentioned but rather accept the official narrative without questions.
Which narrative is that?
EU states can outright ignore EU law, like Hungary does. They won't be invaded, like if a nonsovereign entity like Minneapolis ignores the laws of its sovereign
There's a common thread that the EU is some awful unaccountable organisation. This tends to mainly come from the US. It's also the line pushed by Russian propaganda for the last 15 years.
In reality the EU heads of state appoint the EU commissioners and form the EU council, and the EU parliament is elected by the public. Nothing gets passed by the EU without the approval of the council and parliament, and while it's arguable that parliament is a "rubber stamp" shop, it's certainly more independent from the executive than the US congress is, and the Council certainly isn't. It's also true that any country in the EU can choose to leave the EU at any time, unlike say the US, who refuse the right to self determination of its people.
"Sovereign" is pretty widely used in the space industry to mean "made domestically, including the subsystems".
In this case, it means subsystems made in EU countries, and not imported from outside the EU.