Hi Kris,
I think the first sentence is incorrect, but the second sentence matches what we were trying to say.
The first sentence now says "The start-of-range and end-of-range elements must be leaf <indexterm> elements." That seems to stand alone as an instruction about all ranges, but the point we were trying to address is only for ranges that are specified at the secondary/tertiary level. So – if you are setting up a range for a secondary index entry, the start-of-range and end-of-range both need to be secondary entries. That rule is correctly conveyed by the second sentence in your highlighted section – "If part of a multilevel index entry, the start-of-range and end-of-range elements must be at the same level of the hierarchy."
If we simply delete the first sentence, the second one almost stands alone. Maybe add a new first sentence to clarify the scope of the second ... something like "Index ranges can also be specified with leaf <indexterm> elements, such as a range specified for a secondary index term. If part of a multilevel...."
Thanks,
Robert