Hello,
To start off, here are a couple guides to shed some more light on the Top Domains Section:
Why a domain may not have been selected:
https://www.namepros.com/threads/the-selection-process-for-top-domains.1047414/
Why a specific domain may have been selected in the past:
https://www.namepros.com/threads/why-is-this-domain-name-in-top-domains.1044806/
Members submit domains for consideration to be included in the top domains section here:
https://www.namepros.com/link-forums/add-your-top-domains.407/
If the only domains being submitted for consideration are three-letter or four-letter .com's then that's all there will be when considering any of them in the selection process.
It should be noted, that there are not just three-letter and four-letter .com's in the top domain section. A quick review just now shows a bunch of single-word domains as well and not just in .com (.net, .org, etc.).
For instance:
ReBox = com
Rotting = com
Disposables = com
Troops = com
Paw = us
Honorary = com
Gardens = net
Sweepstakes = org
Sweets = net
And that's just looking at the first page.
Are you suggesting that staff members should go looking through the other marketplace sections to identify domains that could be selected and move them to top domains? Not sure that's a very good use of staff's time, when there's already a submission option for review.
Keep in mind, the domains in that section are dependent on members submissions, so if there are more three-letter and four-letter domains than longer single-words (Regardless of extension) it's due to what members are submitting and staff has no control over what people decide to submit.
You can get an idea about the types of domains that are submitted daily and not selected here:
https://www.namepros.com/threads/reply-with-your-top-domains-for-sale-no-approval-needed.1333470/