You're welcome to disregard my findings
You're not wrong. The sizing of these SUV's is all out of kilter. Due to the branding/naming conventions people assume they are the equivalent. The T-Roc is smaller than the Golf on many practical levels to get Golf levels of practical space you have to get the Tiguan.
All these SUV's simply sit higher, have less boot depth(the length of the opening lip to the back of the back seats) but have a higher roof line so a taller boot...
T-Cross - somewhere between an Up and Polo.
T-Roc - somewhere between a Polo and Golf.
Tiguan - somewhere around the Golf.
Toerag - somewhere around the Passat.
Q2 - somewhere between an A1 and A3.
Q3 - somewhere near the A3.
Q5 - somewhere between A3 and A4.
Q7- around the A6/A7.
... anybody who has (or had) young kids will know that buying a car on boot size and rear leg room is the first thing you consider, and this is my findings.
That's before you throw in other brands and models. The Macan for example is smaller in usable practical space than Q5 but bigger than a Q3.