That is correct.
If different things have the same VAT rate it will only be displayed in the same line (and summed up).
In other words : all the same Vat Rates will be summed up into the same line.
I can see no reason why there should be several lines that all have the same Vat Rate .
Although, due to legacy reasons, it can happen that the text “delivery Vat (or similar)” will be shown instead of just the common “Vat @ [something]%” if the delivery Vat is a distinctly different rate than anything else in the cart