Mine was all PEX, but the air bladder kit that I purchased uses two short lengths of vinyl hose to connect into the plumbing. That's after the pump, though, not before. Tank to pump is all PEX (the whole 11 inches they are separated).
Since the pump pulls a low-grade vacuum to pull water in, a too-soft vinyl line between the pump and the tank might collapse, preventing adequete water flow. (Kind of the same as over-pumping a low-volume hydrant!)
2014 RAM 2500 Laramie 4x4 Quad Cab w/Cummins Turbo Diesel, 2009 Rockwood 2607, and 3 'yaks!
300W of Suntech Solar, a Rogue MPT-3024 Controller, and a Xantrex PW2000 Inverter