That tests ICMP echo requests not name resolution.
>Our test was very simple and we performed 70 DNS lookups
That's not ICMP.
So i would say icmp is good proxy to actual performance.
And is your point that the tested sites aren't popular in Russia?
>for different popular domains (google, facebook, twitter, gmail, etc)
google.com facebook.com and twitter.com are all in the top 50 sites in Russia[1]. And gmail.com is number 6000 globally[2], so it's unpopular everywhere, not just Russia. Popular sites in Russia tend to be popular elsewhere, and vice versa.
[1] https://www.similarweb.com/top-websites/russian-federation