‘Dialing back’ oversized gas furnace? Is it a thing?

We’ve been getting bids to replace an 80% efficiency 4 ton gas furnace with a higher efficiency 2-stage, variable motor 96% model. A couple of companies have come out to give estimates and want to put in a 5-ton unit and “dial it back” because of the cabinet size. Apparently most new HE units have 17” cabinets and our current set-up (with an A/C) is a 21”. I have searched high and low and cannot find anything about “dialing back” an oversized furnace. Everything I find warns against the issues of over sizing but none mention the ability to “dial back”. Is this a thing? Is it a legitimate way of avoiding having to fit the smaller cabinet to the current A/C unit?

source https://hvac-talk.com/vbb/threads/2242577-‘Dialing-back’-oversized-gas-furnace-Is-it-a-thing?goto=newpost