I could be interpreting this wrong, but the regulatory...

I could be interpreting this wrong, but the regulatory enforcement discretion that the FDA is granting to certain foreign exporters isn't approval to export 365 day a year in perpetuity into the US market. It is simply a temporary exemption from requiring the ordinary approvals in order to address the supply constraint brought about from the temporary closure of Abbott plant which is responsible for 40% of the market share of the domestic baby formula market. If you follow that link above it notes the temporary enforcement discretion measures will be in place up until 14 November 2022, upon which time they will be reviewed (i.e. until Abbott Nutrition sort their shit out).

Once the discretion is lifted those manufactures like Bubs Australia and the UK brand (Kendal), I would assume, will have to apply for the ordinary regulatory approvals to continue supply into the US market.