Unsurprising, as the most complex orchestrations in SoB and its sequels are the small-ensemble Brandenburg Concerts; parts are already written, creative orchestration is limited to designing four or five instruments to play them.
On the other hand Pictures at an Exhibition is a piano solo piece. If it has a fancy "synthesized orchestration" Tomita, like others before him, developed a fairly arbitrary adaptation.
It’s a solo piano piece orchestrated by Ravel, who was a master orchestrator.
That’s the point about Tomita - there’s nothing “arbitrary” about the orchestrations. They’re an updated and exotic take created by someone who is rooted in that lush late tonal school of orchestration, but is using a completely new instrument to make original sounds.
Snowflakes Are Dancing sounds a lot more pianistic. The later Tomita albums sound more like attempts to reinvent symphonic music, with some quirky additions. He’s very consciously shaping the music like a conductor would, while painting with evocative sounds - very much not arbitrary at all.
On the other hand Pictures at an Exhibition is a piano solo piece. If it has a fancy "synthesized orchestration" Tomita, like others before him, developed a fairly arbitrary adaptation.