Regardless of any browser, consider that there's probably a half dozen background programs using the internet connection as well. You'll want to install something like a firewall that you can turn on that blocks all connections except from some allowlisted apps you currently want to use. A simple message check from a handful of installed messengers can occupy that connection for a few seconds while you're trying to load something that's much more important to you right now in the browser
(that^ was my situation this morning on ~12kbps 2G network, trying to load my ~4KB grocery list webapp in the grocery store with bad reception... ended up connecting to the store WiFi and sold my soul with a checkbox ^^')
Add in a weather app updating, system update check, some app trying to download a new version, the keyboard sending telemetry or downloading new words, the OS trying to load a "generate 204" page to detect whether there is connectivity, the GNSS subsystem loading SUPL data for positioning, Google submitting its WiFi scan data to either obtain a location or improve their service, calendar sync...