Ok - glad we're agreed. Natural G with high expansion ratios has been of great interest to me for the past years while most others have been 'distracted' with spherical substitution of synthetics. Can't say spherical has ever been of interest to me, namely because barriers to entry seems too high for my liking (eg: time to complete qualification and legislative burdens of moving this type of high purity graphite across borders).
To your point about composite plates being made from secondary synthetic - again largely agree - but I know of an Imerys product where they use expanded as a filler to the main ingredient of secondary synthetic (i.e: potential adding to demand for natural flake more than most people have considered).
Only reason I mention Imerys is because I know they have a majority interest in a Chinese facility that uses hydro power to process their natural flake graphite (with high expansion ratios). I suspect it may be useful to you to incorporate into the costing analysis you posted on the BKT thread about thermal purification.
