I'll re-process my whole elevation dataset (around 300gb / 6 million tiles IIRC)
I was wrong on both counts, it's actually about 9 million tiles but "only" 169 gb. But it involved re-processing 1.7 terabytes of uncompressed source data and when you count all the intermediate files that were created it would amount to about 3x that much data.
Here's another little update, the icon is now blue! Makes it stand out as a special function and is also in keeping with the way that 3d maps are shown in blue on the menu. Also, it's easier to say "click the blue button" instead of giving a long description.