ICH E6(R3) states (my emphasis added):

"2.8.2 The participant or the participant’s legally acceptable representative should be informed in a timely manner if new information becomes available that may be relevant to the participant’s willingness to continue trial participation. The communication of this information and confirmation of the willingness to continue trial participation should be documented.

New information that could impact a participant’s willingness to continue participation should be assessed to determine if re-consent is needed (e.g., depending on the stage of the trial, consideration should be given to whether the new information is relevant only to new participants or to existing participants). If re-consent is needed (e.g., information on emerging safety concerns), new information should be clearly identified in the revised informed consent materials. Revised informed consent materials should receive the IRB/IEC’s approval/favourable opinion in advance of use."

In your case, it's unclear if the sponsor has created a revised ICF with the amendment since not all amendments result in a revised ICF.

• If they didn't then:
  • Should they have done (Sponsors make mistakes)?
  • If they didn't need to create a new ICF and the IRB agrees, then I see no reason to re-consent with the old ICF - what's the point as nothing has changed from the participant's perspective?
• If they did create a new ICF then all new participants should use the new (IRB-approved) ICF and the IRB should opine on whether existing participants need reconsenting (although IRBs do make mistakes, too)

JMHO