As of 1.7, new item id's were added to replace old numerical id's, but an enderman's "carried" tag still uses the outdated numerical tags.

For example, while the equipment tag might look like this:

{equipment:[{id:grass}{}{}{}{}]}

An enderman's carried tag looks like this:

{carried:2}

2 is the old id for a grass block, instead of the new minecraft:grass.