Very nice job, and very clear and thorough WIP instructions.
I was particularly interested in your rationale for using ply rather than MDF. Up until a year or two ago I generally laid a layer of 3mm MRMDF onto ply before veneering. But then suddenly supplies of 3mm MRMDF disappeared. I subsequently tried veneering directly onto ply, it can work but I agree with two points you make.
You need A/B/BB quality birch ply because patches can telegraph through and voids on cheaper ply grades are a problem. And secondly the need to flatten ply. It’s surprising how uneven even good quality ply can be compared to MDF. However I use a drum sander because if you break through the very thin top ply you hit glass hard UF glue which quickly blunts planer knives, also if you do expose the ply glue then PVA will no longer reliably bond to it.
Thanks again for an excellent post and good luck with your new venture!