Do look at other brands, then. I don't think you have to stick with one range. My rangehood and cooktop are F&P, and my oven is Miele.
I chose all my items based on performance reviews (Choice and others), and the company that does the best cooktop may not do the best oven and may not do the best rangehood, etc. And even in cooktops, the best gas cooktop may be a different brand than best electric or induction cooktop.
If they're all stainless steel, or all white, they can still go very well together.
If anything, when I see an appliance package (all appliances branded the same), it just makes me think the person who selected them didn't put any thought into it / didn't research the best products.