You don't get doppler effects off baffle flex the baffle exists to hold transducer to support mid-bass frequency and to limit vibration levels. An over small speaker will require BSC- baffle step correction in its network to compensate if baffles undersize it is why small speakers sound thin. Also aluminum is cheaper by the ton than plywood and it is also lighter why it is used so much over ply it is not better sounding just cheaper to build ship etc.
How thick should the front baffle of speakers be?
Some manufactures advertise or hype a thick front baffle, two layers of MDF, if the woofer is as thin as paper cone how could it change anything. Could be just hype