You can, without talking to a single human being, complete design reviews, claim and fix 1000s of bugs, review PRs, update and ship documentation or releases, etc etc.
Deep Solitary just means "asynchronous", "uninterrupted", and "self-scheduled" in this context.
Reviewing other people’s PR is a collaborative task, fixing bugs "reported by others" is a collaborative work, updating docs and release notes for "other" stakeholder's consumption is collaborative work.
Unless you're building a house deep in the woods for you by you, you're collaborating with other people on different levels.
Let's be honest, introversion is a gradient scale, maybe we've shifted a bit more towards cutting out the office Watercooler talks but everything we do as a species is still highly collaborative.
The definition of collaborative that includes "In person" is just wrong.