Yes. This is still the case in 19.
One way around it is to just include picks of your own to "free space" on your own pick-stockpile for the year in question. In other words, if trading for 2nd and 3rd in 2033 and getting that error, throw in two 7th rounders of your own (which may also allow you to acquire slightly better picks). That may allow the trade to go through. It has (every time) in my experience.