This is an odd claim. Clearly Xeon Phi is the shipping version of Larrabee, while Zen 4 is a completely different chip design that happens to run AVX-512. The first shipping Xeon Phi (Knights Corner) used the exact same P54C cores as Larrabee, while as you point out later versions of Xeon Phi switched to Atom.
It is extremely common to refer to all these as Larrabee, for example the Ian Cutress article on the last Xeon Phi chip was entitled "The Larrabee Chapter Closes: Intel's Final Xeon Phi Processors Now in EOL" [1]. Pat Gelsinger's recent interview at GTC [2] also refers to Larrabee. The section from around 44:00 has a discussion of workloads becoming more dynamic, and at 53:36 there's a section on Larrabee proper.
[1]: https://www.anandtech.com/show/14305/intel-xeon-phi-knights-...