Is an intellectually disabled and death-sentenced prisoner entitled to review under 28-U.S.C-2241 because diligent counsel could not have raised this claim in any prior proceeding?

QUESTION PRESENTED As a general matter, a federal prisoner may only collaterally attack his conviction or sentence by filing a motion to vacate or set aside his conviction or sentence under 28 U.S.C. § 2255. Under § 2255(e)’s “savings clause,” however, a federal inmate may petition for a writ of habeas corpus under 28 U.S.C. § 2241 when a § 2255 motion is “inadequate or ineffective to test the legality of his detention.” The question presented is: Is an intellectually disabled and death-sentenced prisoner condemned to be executed in violation of the Eighth Amendment because he was found not to be intellectually disabled under the outdated diagnostic standards prevailing at the time of his trial and initial 28 U.S.C. § 2255 proceedings, or is he entitled to review under 28 U.S.C. § 2241 because diligent counsel could not have raised this claim in any prior proceeding? i LIST OF ALL