Maybe it can be described as a sqlite bug.
I only use sqlite3 command line, I don't know how it would be the real value using library or api calls. But in command line returning 4.2 and using 4.1999999 in the filter condition is not consistent or could be improved.
either returning in command line
408|41.1999999999|129.727571723508
840|41.2000000001|-73.970001
840|41.2000000012|-73.964172
or using for filtering the same rounding as command line does (4.2)
840|41.2|-73.970001
840|41.2|-73.964172
408|41.2|129.727571723508