Eh-em
It surely comes near to double on the early levels but after a few hours it becomes pretty pointless, If you solo an Level 70 Ultimate say you get 125k Experience Points; You wasted I don't know 8 minutes on it and used 3 Seeds.
Then you go and solo a Level 80-90 Expert, you're most likely getting 70-80K But let's stick to your "words" and say you get half of the ones you could've gotten on Ultimate, even then you only spend 1 Seed instead of 3 and took let's say 3 to 5 minutes to complete it in comparison with double the time it would take to do an Ultimate.
Now then It doesn't seem more productive to farm Points from Ultimate, does it?
Don't get crazy about it though, Expert is better than Ultimate around 2.1 times not thrice as you'd think by the Seed usage when you take in mind the time and also the fact that this is only valid after both are level 40'sh +++