No the only place this is available to any extent is if you're looking at a single user's session where you can see all of the user actions in order but there's no way to get this as a metric or even as number from usql.
With usql you can get start times and end times by querying the user action table but you'd be querying both relevant user actions you can't have data from both of them in the same row. And if you queried from the usersession table you can pull from the useractions but you can't get the starttime from two actions separately, there's just no way to express that.
You'd need to be able to do something like select action1.startTime - action2.startTime as difference from usersession which you cannot do.
Yes. This is very useful information for business, we have useraction.startTime information in the useraction but we are not able to use it wisely for our analysis. Extracting data via USQL API and query the time difference from another tool would not be an ideal way for a single use case(this involves exporting data and requires elasticsearch or an ideal tool in Prod enV).