Sorry, I got mixed up. I answered briefly on WhatsApp. Copying it here:
In my opinion, this is baseless. This should be taken into account when buying an apartment.
What he describes is not a consideration that can lead to a different implementation of Jewish law, but a hardship. Hardship is not a halakhic argument. I discussed this at length in the series on tradition, in the lessons on the difference between Reform thinkers (Moshe Zemer) and the modern model that I propose.

Maybe there is room for discussion within the framework of Jewish law without any changes.
If the reason invalid roofing is disqualifying when there is something else above it is because what is above creates shade, then seemingly if the balcony above is high enough (more than twenty cubits), then that sukkah should be valid, no? Because the upper balcony no longer creates shade over the sukkah.

That wasn’t his argument. In any case, that is not correct halakhically. It is explicit in the Talmud that the height of the invalid roofing does not matter.

Where is that explicit? I saw that some rule in practice that if it is higher than twenty cubits it does not disqualify.

I know that isn’t his claim (by the way, I argued here on the site in the past that he is not committed to Jewish law, and if I remember correctly you said that was conservative demagoguery—I don’t remember the exact words. Do you agree with me now?). I used his argument to raise the question. Which Talmudic passage are you referring to?

From one argument you can’t draw general conclusions. You have to hear what he says in response to the objections raised against him. Sometimes a person doesn’t notice, or doesn’t formulate things precisely. And sometimes he retracts once it becomes clear that he was mistaken. So I prefer to discuss arguments and not the people making them.
As for invalid roofing above twenty cubits: a sukkah under a tree or a house is invalid, and I have not seen anyone distinguish and say that if the house or tree is twenty cubits high, the sukkah is valid. There would have been room to make such a distinction in order to understand sources that validate it without resorting to various forced interpretations. That also seems to be implied by the case of a sukkah in the shape of “Ashtarot Karnayim” at the beginning of the tractate.
I just now saw a reference to Rabbi Ovadia: Yalkut Yosef, Festivals, p. 125; Hazon Ovadia, Sukkot, p. 11. I haven’t looked inside.

And one can also learn this from the law of a sukkah beneath another sukkah: if both have more shade than sun, and the upper one is more than twenty cubits above the lower one, the lower one is invalid because it is a sukkah beneath a sukkah. True, perhaps one could distinguish between a sukkah beneath a sukkah and a sukkah beneath a tree or house, but plainly, if what is above twenty cubits is not a sukkah and not roofing, then even in the case of a sukkah beneath a sukkah it should not disqualify.

So that nobody gets confused: we’re talking about Rabbi Ido Fechter.

Where is there a case written where the upper one is more than twenty cubits above the lower one? If you mean these words: “Sometimes both are invalid—what is the case? For example, where both have more shade than sun and the upper one stands above twenty cubits,” seemingly the meaning is that the roofing is more than twenty cubits above the floor, and therefore the upper sukkah is invalid. But it does not say that this is a case where the upper roofing is twenty cubits above the lower roofing.

See the commentators there (I think already in Rashi).