The chart identifies the ships as star ships, and, thus, the majority of the ships of the Enterprise
-type were docked at Starbase 11 for repairs and maintenance. It's possible that when the Enterprise
visited the starbase, Starfleet was not at war with anyone and Starfleet Command decided to have their capital ships undergo maintenance. I am thinking of Pearl Harbor here where the US Navy decided to berth nearly 50% of its active battleships at Pearl Harbor in the halcyon year of 1941.
I think it was a missed opportunity when the CBS digital team chose not to emulate the Utopia Planitia Fleet Yards seen in "Relativity".