SS Hard Drive with Bluesound Node 2

As an experiment, I purchased a $50 Passport, 1TB, solid state, USB drive, loaded it up with all my hi-rez files and about 100 flac-ed cds, then hooked it up to my B/S Node 2. Using the iphone app, it works flawlessly and sounds perfect.

The B/S user manual recommends against using large hard drives at the USB port, and I continue to see streamer manufacturers using mechanical hard drives, avoiding solid state. Any body known the thinking behind this?