As our understanding changes, our definitions must change.<quoted text>
"our universe is part of something larger: a multiverse."
This writer does not know common definition of words used daily in science.
And you quote him. LOL
Follow the piper.
There was a time only 100 years ago, when universe and galaxy were thought to be synonymous.
The term multiverse is considered appropriate to include entities that may exist outside the domain of our own Big Bang. Physicists are perfectly comfortable with the term and its common usage now.
Get over it. When new ideas form, new words are coined to denote them.