Carb Absorption Question

Sorry if this has been asked before (and I’m sure a horrendously limited knowledge of nutrition) but Nate’s insta carb loading got me thinking.

Accepted wisdom seems to be you can absorb 60-90grams per hour on the bike but what about off it? For example Nate ate 186grams of carbs from oatmeal & blueberries, I’m presuming this was absorbed over several hours otherwise it get turned to fat? Is there a standard rate of absorption while sedentary?

If unused carbs become fat how can you ensure additional carbs in carb loading fill glycogen stores?