If Trump had this presser carefully organized ahead of time--like who he was going to call upon--he could have Sean Spicer prep him on likely questions and forearm him with background info on those to be chosen.
In that case, it's likely that Trump knew of April Ryan's having arranged meetings for Democrats.
Mike Pence says that Trump is very strategic but gives off an appearance of haphazardness.
That’s why he asked her if she could arrange the meeting with the black Caucasians. Totally threw her off guard as he described how he was stood up by that psycho John Lewis!