In plain English
FAR 52.214-24, Multiple Technical Proposals, is a solicitation provision prescribed at FAR 14.201-6(s), most recently dated Apr 1984. The complete official text is reproduced below, verbatim, from GSA's published FAR source files.
Its text contains no sentence requiring insertion into subcontracts; see the flowdown section below for what that does and does not mean.
Does it flow down to subcontracts?
No flowdown mandate found in the clause text
This is a solicitation provision — it applies to offerors when submitting an offer, not to contract performance, so subcontract flowdown is generally not the operative question for it.
Where it's prescribed
As prescribed in 14.201-6(s), insert the following provision:
Prescribing reference: FAR 14.201-6(s).
The official text, verbatim
As prescribed in 14.201-6(s), insert the following provision:
Multiple Technical Proposals (Apr 1984)
In the first step of this two-step acquisition, solicited sources are encouraged to submit multiple technical proposals presenting different basic approaches. Each technical proposal submitted will be separately evaluated and the submitter will be notified as to its acceptability.
(End of provision)