Not sure if anyone noticed but the terms for Exception from Reduction or Offset in relation to §6428 and §6428A are different.  What Bob cited is from the CARES Act in relation to §6428.  Interestingly, Sec. 272(d) of the COVID-Related Tax Relief Act, stipulates the following (emphasis added):

EXCEPTION FROM REDUCTION OR OFFSET .— Any refund payable by reason of section 6428A(f) of the Internal Revenue Code of 1986 (as added by this section), or any such refund payable by reason of subsection (c) of this section, shall not be—
(A) subject to reduction or offset pursuant to section 3716 or 3720A of title 31, United States Code,
(B) subject to reduction or offset pursuant to subsection (c), (d), (e), or (f) of section 6402 of the Internal Revenue Code of 1986, or
(C) reduced or offset by other assessed Federal taxes that would otherwise be subject to levy or collection.

While the CARES Act simply refers to §6428, which covers both the Recovery Rebates Credit under subsection (a) and the Advance Refund under subsection (f), the COVID-Related Tax Relief Act limits this to §6428(f), which only deals with the Advance Refund.

It is not clear if this is an oversight, especially since it is apparent from the structure of §6428A and the amendments to §6428 that Congress intends to make these payments more broadly available.  If it is not an oversight, these would create a bifurcation of the treatments and I'm not even sure whether the IRS' system would be able to cater to that.  If it is an oversight, it may take a technical correction to fix this.