Frank is talking about Tegmark Everett Deutsch Level 3.
Do not confuse that with the string theory predictions that are only for Tegmark Level 2.
Frank's BASIC result is well-known it's in Ch 11 of Murray Gell-Mann's THE QUARK AND THE JAGUAR and in one of Henry Stapp's formulation of Bell's theorem that
1) Born probability rule P = |Psi|^2
2) Counter-Factual Definiteness
3) No-faster-than-light influence of any kind
are incompatible, i.e. not all of them can be true without logical contradiction.
Gell Mann & Tiple assume 1) & 3) are true & 2) is false at it is in Everett's Level 3 multiverse
Stapp et-al assume both 1) & 2) are true. Therefore 3) is false.
However, even the Pundits FUBAR on this point because the precision cosmology evidence that may be explainable by string theory is completely irrelevant dealing only with Tegmark Level 2.
There is widespread confusion & sloppy thinking on the meanings of the single term "multiverse" even by experts who should know better.
The post-quantum theory first professed by yours truly & Josephson (w Pallikari) independently in parallel and now backed up by Antony Valentini's work denies 1) for living matter. 1) still works for dead matter.
However, Valentini shows that if 1) is false then 3) is also false. They are not independent.
Of course, all three may be false without contradiction.