Valentina Shevchenko is callin' B.S. on the reason behind Amanda Nunes' UFC 213 title fight withdrawal ... telling TMZ Sports she's "not believing 100%" that Nunes pulled out over health issues.
We spoke with Bullet about Nunes pulling out due to chronic sinusitis ... and Shevchenko says she doesn't believe the excuse because Lioness seemed perfectly healthy the week leading up to the fight.
As for why Nunes would make up the claim, Shevchenko speculates the withdrawal happened because Nunes was "feeling (her) energy" and wanted to reschedule the fight to throw off her rhythm.
But V.S. says if it was Nunes' plan all along to bail, it didn't work ... 'cause she'll be ready whenever a makeup date is set.