This is Part 2 in a series of posts on formaldehyde. Let's start with a quick review of the two ways to evaluate the use of formaldehyde in a glued wood product: content or emission.
Emission level ratings (most commonly the "E" series in Europe, and also the "F" series in Japan) look at the content based on the amount of formaldehyde emitted from the product that is captured by the specific test method being used. In the U.S., formaldehyde emissions from the unfinished wood panels are captured and measured directly. Most of the global testing methods do not account for the lower emissions rates of finished products, i.e., that the "breathable quantity" is lowered by the overlays and/or finishes applied to the final product. In fact, the formaldehyde emissions from finished goods can often be at or very near the same levels as natural wood. (And yes, even solid wood emits formaldehyde at measurable levels!)
The formaldehyde emissions from finished goods can often be at or very near the same levels as natural wood.
On the other hand, content ratings restrict what can go into the product at all. There are two content ratings: "no added urea formaldehyde," which allows phenol formaldehyde or other forms to be used in production; and "no added formaldehyde," which does not allow phenol or any other types of formaldehyde at all.
Some organizations (like LEED) use content standards, believing that just having urea formaldehyde present at all is a problem. LEED requires composite wood products to have "no added urea formaldehyde" while some other groups go even further and require the elimination of ALL types of formaldehyde.
There are three possible reasons for this policy. One, most emission standards are based on an average emission, and therefore some individual panels or boards might be higher than the stated level. Two, there are multiple ways to test for formaldehyde (even within one rating system) and different standards are not always interchangeable. To eliminate any discrepancies or confusion, some organizations simply state "no added urea formaldehyde" or "no added formaldehyde." (I suppose you could consider this a "lazy" way out, since they don't have to understand the science or the standards, just ban the chemical completely.) Finally, three, although there is no established studies that I have found on these points, they may be concerned that a surface barrier could break or wear down over time or that a chemical blocker might eventually fail.