OP wants a bike cover to protect his bike, period... Telling him that his bike can handle rain or be dirty is not very relevant to his enquiry on this forum.
My race bike does not (never) see rain, dirt, sand, salt, etc. Not because it's not capable of, but because I baby it and I specifically bought a gravel bike for spring and rainy days. I am sure a Ferrari can be driven in rain or even during a cold harsh winter, but people choose not to do it and it's OK.
Let us know if you end up buying that stretching bike cover and how it holds. I know high speed wind can be a PITA with covers...