TESTING DIFFERENT DECKS AND ARM COMBOS

Just for discussion purposes I am posing this.

Many people that review - nay almost everyone - says that when testing a component against another you do a direct comparison without changing a thing save that component therefore same everything but the cartridge or tonearm.

I have wondering if this is a bad approach or not as I am contemplating a bake off at home. My EMT is optimised for an EMT 929arm and EMT cartridge; Amazon Model One Transfiguration; JVC QL10 (not sure but i reckon good mm so Pickering XSV4000); Townshend Rock (london decca - sadly not got one)

My rationale is that lets say you race a car rounda track you don't put Porsche 911 tyres (including the wheel and tyre) onto say a mercedes CLK - yes it will work but it is not optimised.

I am not a reviewer - but that said I think the whole front end optimised approach is the best. What say you and why?