Yeah, I noticed this yesterday when I saw 3 apps being downloaded and updated simultaneously.
One downside I noticed was play store became too slow to do anything else and super glitchy – like pressing the update details button didn't do anything. The animation was slowed down and I couldn't load anything else in a jiffy.
When it finally started to accept user inputs pressing back it was existing the updates page and still being on the updates page. Apparently, it opened the updates view multiple times I had to close the play store app and re-open to fix the issue.
So, while it can do simultaneously updates its not glitch free and has bugs in general.