Hmmm...first thing I wanted to look for in this playtest pack is if indeed the last playtest release (with magic items) was working off of a different iteration of the stealth rules; eg perhaps the next iteration decouples Listen and Spot from Perception and makes them separate skills. Sure enough, this playtest does so. So then, it would appear that, at first glance, the Boots of Elvenkind were working off of this current playtest's Perception rules and, as such, were not completely incoherent.
However...one problem...
While the current iteration breaks out Listen and Spot from Perception, it does not break out Hide and Move Silently from Stealth (now Sneak). So I still don't know what The Boots of Elvenkind do. Do they give disadvantage on Listen checks to detect a Stealth (Sneak)er in a contest? Do they give advantage on Stealth (Sneak) Rolls? Is Stealth (Sneak) supposed to be broken out into Hide and Move Silently and you get advantage on Move Silently Rolls (or you automatically succeed at a contest versus Listen)? I don't know.
So I look to the Stealth Rules for a clear, transparent clarification on Stealth Rules and how Listen, Spot, and Sneak all interface with each other in a contest to determine detection or successful detection avoidance. Reading them, I have no idea. There is lots of fluffy text ruminating upon Stealth Requirements and Perception protocol. One section under Perception even speaks (albeit somewhat implicitly) to Stealth contests - "Noticing a Hidden Creature". Within that collage of words it says that [paraphrased] normally your Stealth check is a mix of looking and listening, so you don't need to be too specific in your description. Ok. But what does any of this tell me about the actual mechanical resolution of the contest...specifically when we now have Listen and Spot broken out of Perception but still have Hide and Move Silently abstracted into "Sneak". How about something concrete like: "If you have the Listen or Spot Skill, you use that Skill Bonus in Stealth Contests to detect someone using Sneak to avoid detection." Perhaps they have Hide and Move Silently broken out of Stealth (Sneak) in the next iteration and this one is, as the last Stealth rules were with the magic item release (Boots of Elvenkind), are incoherent with Listen/Spot:Sneak contests. I guess this is Rulings not Rules?