That seems to be a custom Google API, not DNS over HTTP(S). Request format is very different from what is specified in https://www.rfc-editor.org/rfc/rfc8484 (/dns-query?dns= followed by raw DNS bytes). But sure, the implementation could easily be changed to use DoH

Whether it can technically be called a DNS request or not, this is a privacy leak for anyone who isn't already using Google as a DOH provider. So this should really be written on the extension page...