If not the 19 inch standard, then why not the 23 inch standard?
The 19-inch (482.6 mm) rack claims their origin as mounting systems for rail-road (railway) signalling relays, It has served many industries well. It's even used in ships.
If this minor league server centre player is unhappy about 19 inches, why not switch to the 23-inch (580 mm) standard which even the EU recognises as the ETSI rack, relating to the European Telecoms Standards Institute.
The vertical spacing is identical and the 19 inch adapter pates are commonly available.
It appears that Facebook's Frank Frankovsky doesn't know his rack hardware too well.
Finally, if the 19 inch isn't satisfactory because it gets overfilled, why does Frankovsky the larger standard won't suffer a similar fate? Don't believe me, just go check-out an airport baggage carousel.