Seriously, do you really think that something that cannot be worked out over slack/confluence/phone call can be worked out in person sitting in the busy office with all kinds of distractions and stress caused by commute in/out....
The most efficient way to communicate specs is through a document, so I have something to reference. I'm not going to remember everything said in a meeting unless I immediately start working on it. The spec document should be exhaustive, clear and easy to follow with no dangling questions unanswered.
If you can get a spec writer that can do that, you're golden.
Not only is the 5% important, as every "only 5% left" tends to be, you are completely ignoring possible developer questions.
You do realise you do actualy need some form of requirements, otherwise what are you doing, just writing code with no goal?
Granted it doesn't need to be a big up front document, but some of those slack/confluence/in person meetings will ultimately be around "so, guys/gals for this next proposed , feature, story (requirement), w/e, this is how I'm achieving it". Oh, and as for non functionals..
Having spent years working remotely with office focused teams, the nuances of these discussions are the ones that get missed by the remote attendee unless everything is set up correctly.