Burden proof that a character has an ability is on you, not on me. "He casually wasn't on guard in the anti feat" is not proof of FF having an ability he has never shown.
Obviously. If you see a character having a technique where without being there cuts a place, then the character suddenly disappears saying "Let's wrap it up and leave promptly", being an intelligent ninja like FF is, it is obvious he could deduce he'd use such a technique.
Your argument is that a ninja that never have witnessed spatial manipulation techniques besides, at best, Blast's once and has not shown he can detect them can detect an ability that he has shown to fail to detect previously when other characters with a true ability to detect it (Blast) could.
Edit: Btw, this also contradicts he not noticing Blast warped to where he was to follow him. Meanwhile, characters who truly could detect alterations on space like Blast and Tatsumaki could detect spatial alterations without being concentrated on doing so.