There's a known issue with slow page loading with Woocommerce ajax get refreshed fragments, as outlined here: https://www.webnots.com/fix-slow-page-loading-with-woocommerce-wc-ajaxget_refreshed_fragments/
WP Rocket is able to optimize this request.
Can you get Hummingbird to do the same? On my site it is taking 2.8s to load. I can't disable it on the home page as I have products there.