The problem with adding the spaces is that it makes our tables wider than the amount of space that Wikia allows, thus making that pop-out button appear more often on more of our pages with these tables as a result.
P.S. If you mouse-over the build times on the tables, I did make the tool-tips say
# Years, # Months, # Days # hours, # minutes and/or # seconds
I think you used the wrong ISO reference because ISO 1000:1992 standards were withdrawn in 2009 in favor of ISO/IEC 80000-3 which is based on ISO 31-1, the part of international standard ISO 31 that defines names and symbols for quantities and units related to space and time.