In a Facebook post:
They don't come much bigger than this ... Our guest singer this Tuesday tunes is a blue whale. Just click on the link below to hear its song. #BiodiversityMonth
–Australian Department of the Environment and Energy, 20 September 2016
In Collins Dictionary:
I like a big challenge and they don't come much bigger than this.
–Collins COBUILD Advanced Learner's Dictionary | 8th ed (En-En), "challenge"
My understanding: This sentence is used for emphasizing something. In the first example, they refers to other whales. In the second example, they refers to other challenges.
Is my understanding correct?