You get XP for any kind of driving in this game, across all the modes.
But I feel like the amount of XP that you get for driving in time trials
(high concentration, edge of your seat, no blinking, giving your very best) is pretty small in comparison to everything else.
And getting XP based on the amount of completed laps feels a bit unfair if Spa is ~7 km long and Monaco is a bit over 3 km.
I would just love that for the same amount of driving time, you go away with similar amounts of XP.
Of course things like taking a race win should get a bonus reward, but you can always win a race,
but it's hard to always beat a new personal best in time trials.
Maybe I'm wrong, please let me know.
(Maybe it doesn't matter, and I have everything unlocked in 2 weeks either way. I dunno.)