Playing before fully updated?

I heard you can click Play while the download bar is still at Orange, but it might cause glitches. I heard that years ago though. Is that still a problem?

EDIT: I already did it briefly, but quit to be safe. After I quit I had about 400 MB left to download, but before I started I had well over a gig, maybe nearly 2 to download. Should I be concerned? I’m surprised it went that fast when its going so slow now (only kbs/s atm).