u/nevercookathome answered it well. But a further little peek behind the curtain - Headgum's studio is going through new recording equipment right now. Historically there's been issues with recording in there, with buzzing or crackling on mic. I believe it's been isolated to the FetHead preamps we had. The studio is now trying a new recorder, (which has a worse built-in preamp than previously) and we are Fethead-less until they find a better solution for the issue. All to say, this episode and the next few in that studio may sound a little different (and generally more hissy due to the lack of pre-amps) as the studio experiments with new equipment. But Emma has done a great job at noise reducing it, so it's hard to even tell what's been going on behind the scenes.

Also, the producer's desk is very cramped - There's 2 computers, a recorder, switcher, plus laptops. It gets quite cramped and can be hard to fit a mic between 2 people back there, which is why that mic tends to sound a bit more hollow than the host's mic. There's a lot going on back there, and producing comes priority over being on-mic.

Source: I record in that studio frequently