In plain English
FAR 52.232-11, Extras, is a contract clause prescribed at FAR 32.111(c)(2), 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
We scanned the full clause text and found no sentence directing the contractor to insert this clause into subcontracts. That is a statement about the text, not legal advice: a prime contractor may still flow terms down contractually, an agency supplement (DFARS, VAAR, …) may add requirements, and clauses listed below (if any) may order this clause into subcontracts from the outside.
Where it's prescribed
As prescribed in 32.111(c)(2), insert the following clause, appropriately modified with respect to payment due dates in accordance with agency regulations, in solicitations and contracts when a fixed-price supply contract, fixed-price service contract, or transportation contract is contemplated:
Prescribing reference: FAR 32.111(c)(2).
The official text, verbatim
As prescribed in 32.111(c)(2), insert the following clause, appropriately modified with respect to payment due dates in accordance with agency regulations, in solicitations and contracts when a fixed-price supply contract, fixed-price service contract, or transportation contract is contemplated:
Extras (Apr 1984)
Except as otherwise provided in this contract, no payment for extras shall be made unless such extras and the price therefor have been authorized in writing by the Contracting Officer.
(End of clause)