I'd agree that demand far outstrips supply without question. PS5 is supply-constrained everywhere and Japan is one of the worst off. However, with the supply so small it's hard to say how big demand actually is. The 30x the weekly amount could be the extent of the demand or it could be only the tip of the iceberg. Trouble also comes considering that PS5 is supply-constrained everywhere and some of the Japanese demand could be resellers for the East Asian market outside of Japan.
This is where software sales enter into it, because even the highest selling PS5 game has a less than 10% physical attach rate and the beginning of a console's life is typically where the attach rates are highest. Now, that factor is complicated by digital sales and backwards compatibility with PS4 titles, but then PS4 titles are declining in sales rather than increasing so that seems unlikely. Digital titles are the big question as I haven't seen numbers on those, but in general the PS brand has been on a decline in Japan since the PS2. PS4 bounced back a little compared to the Vita, but the Vita was so mismanaged that that's no surprise. I don't think the PS5 will crash and burn, but another decline from PS4's 9.4 million to about 7-8 million seems reasonable.

Wait I don't understand
Some people are trying to say there is not much demand for the PS5 in Japan because it doesn't sell many each week, even though every single PS5 that gets shipped there is instantly sold out.

With this lack of intelligence, one has to wonder how that manage to cross the street without getting hit by a bus

Can we get a chart that shows ps3, vs ps4, vs ps5 in japan
I feel that if we can see how all 3 are comparing to each other we can get a better guesstimate of the ps5's projections rather then just arguing with each other about what and what isn't reliable data

If I recall correctly the ps4 is at the low 9 millions while the ps3 is around 10.5 million, and we all know how slow the ps3 started off

>>MAYBE!!!<< (What If... From marvel should hire you)

Wait, what? but you were the guy who said a moment ago that people loves backwards o_o7  And now you say they want to play them in ps5? 

Besides, that does not respond to my question, why the ps4 version of all those games (PS4 has 9M of consoles in Japan) does not have more decent sales.  Some of the neither pass the 100K copies... It is very lame, and about this, I am sure it is not the stock

The backwards capabilities games aren't ps5 versions. You seriously don't think people don't lose interest on a console that is almost 10 years old? If we don't lose interstate why bother releasing new consoles? The games you mentioned elden ring, horizon, RE8, FF and Death Stranding they would rather play the superior version and that is the ps5 

Ah ok... So, in conclusion... Low sales of Playstation games in Japan is fault of people who wants to wait who knows how many months to buy the ps5 and playing the same game of the Ps5 version that they could be playing in ps4 right now... And for that... the PS5 will sell more than switch if the stock issues did not exist...

Cool........... I say again, I think Marvel is hiring writters right now

You expect ps4 games to keep selling millions? Many have lost interest in the ps4 because it's 9 year old. They rather play these new games on the ps5 because of faster loading times, better graphics, frame rate and controller features. Why do you think the ps5 and xbox series keep selling out when there's hardly any exclusive next gen games? On ps5 I could only think of ratchet, returnal and demon soul remake. On the xbox series there isn't any exclusive 

You misunderstood.

People are saying that not because of it's weekly hardware sales but because of the lack of software sales. It does not look like a very healthy ecosystem.