I think if you secure it down tight to deck it will give you stability and shouldn’t get fly line trapped. I am getting a brace to go around mine about midway up and it will have an adjustable back brace to lean against.
My last skiff had Yeti tie downs and a 35 with Sea Dek up front and a center console bait well/insulated cooler. After about a year, with the center console and the Yeti, I basically ditched the Yeti and added a platform as I got tired of the extra weight of the yeti, moving it around and keeping it from scratching my bulkhead. So, if you don't need a cooler, I'd add a casting platform. If you need cooler space, add the cooler. Don't leave the cooler strapped down when running rough water or most likely, the screws will pull out. Obviously, through bolts are superior. After fishing a variety of deck set ups last week, my big question is what is optimal for elevation and how to manage fly line in Texas winds? I've come to like toe rails, no casting platform and a line tending mat (needs to be heavy enough not to blow) for the simplicity. Once you are elevated, line management can become more challenging and I can see why folks mount a stripping bucket on the casting platform!