Honestly I was expecting higher

This is pretty cool! I like that it shows you the episodes of "down time".

is the appropriate comparison TCP/IP uptime?

i'm just trying to understand how could a "protocol" actually go down beyond the initial client bugs

TCP/IP doesn't have consensus.

IMO a better comparison would be the "uptime of a democracy". Democracy is a governance protocol with consensus.

Maybe there are moments after an election where it is unclear who won.

If that state of confusion lasted long enough, the democracy would be "down" and the society would operate some other way until restored (or not).

i think we both agree that uptime of bitcoin can't be compared to uptime of a data center... but still struggling to find a good comparison to benchmark bitcoin against

Cool to learn about