EDIT: Looking into it, seems the tab memory viewer is only looking at the page and does not take extensions into account; if the extensions inject JS/Style to the page then it counts, and Bitwarden seems to only add a small amount of JS to find password dialogues. It uses memory, but outside of the tab viewer.
Do you use browser extensions? Perhaps they are adding to the memory usage (?)
Only bitwarden (no ad-blockers or anything).
https://sh.drk.sc/~dijit/hn_tab_extensions.png
EDIT: Looking into it, seems the tab memory viewer is only looking at the page and does not take extensions into account; if the extensions inject JS/Style to the page then it counts, and Bitwarden seems to only add a small amount of JS to find password dialogues. It uses memory, but outside of the tab viewer.