I have doublechecked that all other packages that still depend on boost1.67 are all marked RC-buggy and pending autoremovals with various dates.
kig is not an exception, and is treated the same way as all other packages still using boost1.67. since kig rebuilds against boost1.71 were successful prior to starting the transition, it was unknown to boost maintainer that it is buggy. But nonetheless kig alone, does not warrant for boost maintainers to keep boost1.67 in the archive. -- Regards, Dimitri.