1. Because chrome is too large for github. There are a number of infrastructural reasons (bots) that require chrome to be hosted on googlesource.com. 2. Because chrome is not a standalone git project, rather a collection of hundreds git projects linked into each other via DEPS files.
Back in the days submodules where not a thing, and still today they don't cover all the use cases we have in depot_tools. Also the user-facing cli of submodules is the terribly awkward. Not that the rest of the git cli is a piece of beauty, but submodules always remind me of https://xkcd.com/1168/
You can't just git clone chrome, sorry. The project is just too big and changing that now is just too expensive. What would be the concrete benefit?
Going back to the original question, you can get a verbose output if you gclient sync -v, but that would be just too verbose and you still won't infer the overall progress. Because you have no idea which of the hundreds subprojects you are fetching. So when it says "30%" you have no idea if the current project that is being fetched at 30% is 1/100 or 99/100.