Nothing has changed in regard to this. Code 4G implies a distribution from a qualified retirement plan like a 401(k). A distribution from such a plan is not permitted to be rolled over to an IRA for the benefit of the decedent's estate.
The IRS web page that you referenced is incomplete with regard to this in that it fails to specify that only a designated beneficiary is permitted to do such a rollover and that only an individual can be a designated beneficiary. See 26 U.S. Code § 402(c)(11) which only allows such a rollover "on behalf of an individual who is a designated beneficiary (as defined by section 401(a)(9)(E))." Also see 26 CFR § 1.401(a)(9)-4 Q&A-3 which says "only individuals may be designated beneficiaries for purposes of section 401(a)(9)."
IRS Pub 590-B provides information on distributions from IRAs. A rollover from a 401(k) is not a distribution from an IRA. If the account was instead an IRA, an IRA of a decedent can only be moved to an inherited IRA for the benefit of the decedent's estate by nonreportable trustee-to-trustee transfer, so no Form 1099-R would be generated. Code G can never apply to distributions from a decedent's IRA. (Some banks mistakenly use code G for a trustee-to-trustee transfer of an IRA even though the use of code G for such a transfer has never been correct. They should have been able to figure this out at some point in the over 40 years that trustee-to-trustee transfers of IRAs have been permitted and nonreportable.)
