Why Kutaisi to Tbilisi route seem longer, why not from Khashuri? Is there construction work?

My guess is: mountains. Shorter line doesn’t have to mean shorter distance.

The reason is probably that rikoti is sometimes used to be closed at night for regular cars because of construction and flooding and google has been wonky since. If you put your departure as morning, it will show you khashuri route.
Sachkhere road is pretty garbage (at least ot was last year and I don’t think they fixed it). It will take longer than it says and you’ll have a bad time.

There’s been some major landslides there recently by the construction sites, most likely related to improperly conducted geological surveys. The section Vertkvichala-Rikoti is highly doubtful at the moment, nobody knows if it will need to be completely replanned and rebuilt or if they will just pretend nothing is wrong and push through hoping to avoid any political fallout. Last year they closed the highway at night as a precaution when the same thing happened and I guess they might be doing the same this year

But long story short, always remember when you are driving through that masterpiece combo of Chinese engineering and Georgian corruption, you are taking your life into your hands especially in the rainy seasons