I had just realized the update to the R&D page and at first I was excited until I saw how the feature functioned. It appears to only select a specific item and you have yo know the exact quality percentage in order to select said item to scrap it.

A suggestion would be to filter the items rather than select the one you specifically type in. 

Example set to AK-47 >50% and it displays a list of just AK-47s from 50% or below. This would help unclog scrap piles and make bulk scrapping easier to navigate without scrolling through dozens of other weapons you don't wish to scrap.