Thanks for spreading the news!

I'd have 2 quick remarks to clarify things a bit:

The Business Hours Block isn't new, it was added to Jetpack a few months ago, in version 7.1. The 7.4 release just polishes the design of it a bit.
The WhatsApp button is also something that's been in Jetpack for some time, since 2016. The button didn't work perfectly in all browsers though. This release fixes that and makes sure the button can leverage WhatsApp's web interface when necessary.

I couldn’t figure out a way to add text to label what the hours mean.

That's a good idea for a future iteration. I've taken note of it, thank you!

Also, depending on the theme, the alignment displays incorrectly.

That's indeed to be expected with some themes. The block comes with some basic styles that can be overwritten by themes so one can customize the look of the list of Business Hours on their site.