That's an interesting story.
So what was the reaction to the trousers role Ratmir in Glinka's incredibly (to my ears) Russian "Ruslan and Lyudmila"? Was that OK because it was not a self-consciously French trousers role?
It's an interesting question

Of course, we don't know exactly which "whispers" Balakirev was spreading... and the "Mighty Handful" had to remain repectful of Glinka's work, since they held him to be a kind of father-figure. But as you rightly say, Ratmir's music (and the whole of R&L) are very consciously written in a newly-forged "slavic" style (although the earlier works of Bortnyansky, Dargomyzhsky & Fomin were largely and unfairly glossed-over). It's probably fair to say that OPRICHNIK does have a very different (and Frenchified) "sound" to the rest of Tchaikovky's work, though. Basmanov's aria to Morozov (the title-role Oprichnik) "No, no, you need not die!" is something of a endurance-test for mezzos*, and leads into an astonishing mezzo-tenor duet. Personally I love it - but Tchaikovsky left this style alone in the future, sadly. OPRICHNIK is mostly known only for the showpiece "caged songbird" soprano aria for Natalya
Poslyshalis' mne budto golosa, which is pretty-enough as a concert item... but conveys no impression at all of the grim and murderous story of dastardly medieval revenge

* very often it is heavily cut - even Tchaikovsky's own choice of conductor for the premiere, Eduard Napravnik, introduced extensive cuts throughout the opera.