I don't see how they're able to turn "Ukraine successfully conducted a combined arms assault without exposing any of their troops to enemy fire" to "Ukraine has massive manpower shortages".
Like yes: Ukraine is outnumbered. That doesn't change the fact that if you can conduct successful assaults without exposing your troops, that is infinitely preferable to exposing your troops in dangerous ground assaults. Ukraine may be outnumbered at present, but even if they weren't, they would be choosing to conduct unmanned assaults when they can, because they care about preserving their soldiers lives.