Don't see the Russian claims about their RCS there, or the figures for the F18 after the "as required" add-ons, presumably intake RAM etc.
Once again, Google is your friend. Google "Frontal RCS XXX" (where "XXX" is the designation, such as F-22, of the aircraft of interest) and you will get many hits.
Seems an unsubstantiated claim and a weasely attempt to slide out from under.
It's sad that some people are Google impaired. Sadder still is that those so impaired resort to name calling to publicly display their impairment.
For the Google impaired, another link (this one specific to the T-50):
Sukhoi's patent of the T-50's stealth features cites an average RCS of the aircraft of approximately 0.1-1 square meters.
https://en.wikipedia.org/wiki/Sukhoi_PAK_FA#Stealth