I can only agree with your assessment, and thank you for sharing your knowledge of the official dimensions of the boot area

Specs state -
Boot capacity to parcel shelf = 377 litres
to roof = 443 litres

With rear seats down -
to parcel shelf = 924 litres
to roof = 1164 litres.

Or, as others have said, larger than you might expect and certainly large enough for any average family.

I wouldn’t be surprised at that though I’m not familiar with the Yaris!

Noticeably bigger than the Yaris, our previous car

I tend to agree! The boot space available seems larger than you would expect in a car of that size!

I don’t know the exact dimensions either, but I find the boot space perfectly sufficient for my needs having 2 children!! It’s bigger than I thought it would be

I must confess that I’m not aware of the actual dimensions of the boot . However, I personally find the boot area sufficient for my needs! I’m a golfer and I find that all my equipment fits the boot space, especially when the fold down rear seats are taken into account.