Why doesn't speedrun mode skip the TV calibration thing?

Speedrun mode doesn't enable settings automatically, it just disables and grays out cheats and some quality of life changes decided by the community. If you want to enable certain quality of life enhancements or settings like the one you mentioned, you need to enable it manually.

To enable the setting to skip the tv settings screen go in the settings to the Interface tab and scroll to "Skip TV Settings Screen" and enable that.