* Emotional Attachment - not really demonstrated in most cases, and even potential cases can be questioned. The emotion is likely not the emotion of attachment to the object itself ; The object's meaning may be - association with another person or context, and perhaps emotional attachment to that, or simply the memory of it being significant ; The observance of a person's protocol vis a vis the item ; Closure ; Completeness ; Material ; Information Content ; etc. The emotion / distress displayed when demanded to discard is more likely associated with the stressful situation ; the coercive nature of the demand and the situation ; conflict between one's decisions and those demanded.
* Difficulty Discarding - authors pick the most "shocking" objects, and/or those the person decided to keep ( "Magician's Trick" ) - the difficulty is not discarding, it's complying with an unreasonable and arbitrary request that is against one's decision. Let's see client's kitchen garbage bin / recycling, see how they discard something they really see no value in - is there any difficulty ? If not, then difficulty is not with discarding, and the whole thing a misnomer. This also contradicts the "regardless of the actual value" clause from the DSM-5 definition.
* Difficulty Making Decisions - Depends on the situation. If this is referring to the "decision" to discard, it's usually a "decision" made by someone else, and the problem is coersion / reluctance to comply, not any "decisions" per se. Of other decisions, it may be a lack of a decision-making skills, including tie-breaking ( coin toss, feeding the Buridan's donkey ), acceptance of errors / "satisfysing".
This is what we see in "hoarding" books.
What we do NOT see is any of these traits clearly and unambiguously demonstrated, much less universally prevalent.