This does provide a very useful feature for confident, quality engineers: Whenever someone asks for your github ID as part of the hiring process, you can say "Next!"
Seriously, you're an engineer. You can be choosy. And signs of pointy-haired boss syndrome are a good way to choose.
This is one of them.
The correct way to interview someone is to have a stakeholder in the business, who is a competent engineer, look thru the resumes, pick the ones they want to meet with, and bring them in. Talk to them, one on one, for about 30 minutes. (You should know after about 5 minutes, but you want to give them more time so they don't feel like they're being brushed off if you aren't willing to give them the job right then and there. Also, be ready to make an offer, or tell them you'll be making an offer, right then and there.)
If your startup doesn't have a stakeholder in the business whose competent enough to do this, then you still need your technical cofounder. Your technical cofounder cannot be "too busy" to interview engineers.