Oh that was the whole addon, sorry. The usage links on curse were dead, so I just did a LoadAddOn the whole works.
That said, after some digging:
LibPeriodicTable-3.1-Misc by itself untouched appears to take up 115k after a garbage collection.
The data is stored sequentially so it's safe to compare to the 4k table above, meaning it'd take about 28 addons that need to discern flying mounts to make memory usage favor all 28 addons using LibPeriodicTable-3.1-Misc. And each addon that creates a lookup table like the first would need to create its own copy, removing the shared usage benefit of the table. In the
usage page on wowace the example code caches the data into a table the calling addon creates. Every addon that uses that code is going to have a separate table of the same data.
But there's a lot to be said for one central place this stuff gets updated, so only one author needs to maintain the table instead of 28.
Still, getting that bitfield back would be very nice.