It is most certainly not intended behaviour. Writing the exact same argument works perfectly fine in the /wsserver - like it should. Besides, the command itself doesn't work no matter what. A broken command cannot possibly be intended behaviour.
I can confirm this is an issue. Since 1.9 the particle command has no output. I have tested this on both Windows 10 and Android.
It is most certainly not intended behaviour. Writing the exact same argument works perfectly fine in the /wsserver - like it should. Besides, the command itself doesn't work no matter what. A broken command cannot possibly be intended behaviour.