That’s pretty much it. Without the rye to temper it, the corn’s natural sweetness comes through cleaner. I like Maker’s as a sipper, but it makes a crappy Manhattan for that reason.
Sometimes though, I like a crappy Manhattan. If I want something spicy and rye led, then that’s what I want, and I will sip it and savour it. But if want to swill down Jack stirred up with Martini Rosso, then nothing else will do!
Yes, but then what you have is a Queens, not a Manhattan. 
Or a Blokehattan, as it’s known in our house…though I concede you need a feel for British slang for that to actually chime.