Why is Chrome queueing up requests when using HTTP

Question

I have a site that is using HTTP/2, and the site is slow to load images. Looking at Chrome's Devtools, most of the time is spent in "queueing" the network requests for the images. My understanding is that with HTTP/2, multiple requests may be made simultaneously over the same TCP connection, but I am seeing that Chrome is only issuing 6 requests simultaneously and queueing the rest (as if it were using HTTP/1.1). I know that it is using HTTP/2 since the "protocol" column in the "Network" tab says "h2".

Why is Chrome queueing up these requests instead of sending them in parallel?