The EPA and IARC relied on different kinds of research to reach their conclusions. The EPA (U.S.) states that glyphosate is not likely to cause cancer in humans. But, the International Agency for Research on Cancer (IARC) has classified the chemical as "probably carcinogenic to humans."
Also, not all glyphosate products are the same. And in the US at least we only list the so-called "active" ingredients, but the unlisted ingredients can potentially be toxic, carcinogenic, or teratogenic. Generally chemicals get pulled being unlisted when there is little doubt of their harm, but the default in US markets has been to essentially assume every ingredient already on the market is safe. (contrary to the rest of the sane world)
So we get formulations like Roundup which can have various dyes, foaming agents, thickeners, etc to improve the performance and application of glyphosate.
But we often don't know what those ingredients are, unless they are flammable, then those ended up on the MSDS.
For example, Roundup Pro is: 50.2% glyphosate and 13.0% Surfactant blend (proprietary).