> Chrome used to run different tabs as threads of a process but that ended since Spectre and Meltdown. Back to single process since then.

Chrome supports several different process models, apparently, but as Spectre/Meltdown (as well as future renderer and UXSS bugs) mitigation it now by default runs a minimum of one process per site/origin (site isolation). See https://www.chromium.org/developers/design-documents/process... and https://www.chromium.org/Home/chromium-security/site-isolati...