Pretty simple, as a sitter you cannot finish immediately for free when a building takes 5 minutes or less if gold priveledge is disabled.
for those who don't know, the timer goes green to make it easy to see at a glance it can be done for free. If it takes longer than 5 minutes it requires gold to do (hence why there is a block in the first place)
Seeing it costs nothing though, i can't see how this is a gold option. Not the biggest problem but i would appreciate it.