The burden of proof is on the accuser, not the other way around. If you'd like to make a point, than it's upon you to provide evidence, not demand people find the obscure evidence. Secondly, your goal posts have changed, your initial point was not that WAR devaluates relievers but that it devalues high-leverage relievers. I really do want these articles. If they're as easily found as you claim they are, simply posting a link to them would be quite easy.
What I can say is I did what you suggested and googled, exactly "War Undervalues Relievers". The top result was from fangraphs, so I guess we're using fWAR (awesome, that's my favorite!). The article states this:
https://blogs.fangraphs.com/war-and-relievers/
The article can be found at the link. It does not seem to support your premise, however. As stated, each batter is more critical, but this is actually accounted for in fWAR. This means that fWAR does not misinterpret high leverage relievers.
Now, there is this article:
http://camdendepot.blogspot.com/2017/04/why-war-based-systems-underestimate.html
But the issue is this; it's written after the Fangraphs article and quotes a 2010 article. We can see that in this quote, here
So while I think the article is getting at what you want, it is using pretty outdated information. Fangraphs itself, in 2018, claims that leverage is handled in fWAR, while this article, using data 8 years previous claims it's not.
Should there be an article I should be looking at more in depth? I'd be glad to read it.