[defrost]

From your link:

SECTION 11. TOXICOLOGICAL INFORMATION

  IARC No component of this product present at levels greater than or equal to 0.1% is identified as probable, possible or confirmed human carcinogen by IARC.

  ACGIH No component of this product present at levels greater than or equal to 0.1% is identified as a carcinogen or potential carcinogen by ACGIH.

  OSHA No component of this product present at levels greater than or equal to 0.1% is identified as a carcinogen or potential carcinogen by OSHA

> warning for formaldehyde.

Trace amounts can possibly sweat out in specific conditions .. which is why you might choose to install with a vapor barrier.

[inferiorhuman]

  Trace amounts can possibly sweat out in specific conditions

Nah, it's pretty well documented heat and humidity will release formaldehyde. In paperwork filed with the EPA arguing against new limits, an insulation manufacturer trade group cited California's (OEHHA) exposure limits on formaldehyde as reasonable.

Those limits are:

  recently manufactured products contribute no more than 9 µg/m3 of
  formaldehyde into the indoor air

So the Prop 65 warning certainly seems reasonable from here.

https://downloads.regulations.gov/EPA-HQ-OPPT-2023-0613-0230...

[defrost]

Vapor barriers limit human exposure, it has to travel into the occupied spaces to be an issue, then linger.

It also has to be the type of wool that has been treated, etc.