Maybe it should just go to documentation as a limitation. It is unfortunate however if it keeps returning "1" rather than some non-natural number.
Consequently, ERROR_INDEX from
MDEV-10075 is not calculated for table value constructors, either.
I"ve set affected versions to 10.3+ because that's where table value constructors were introduced, and surely the number is not calculated in 10.3 either; but the test case above is only applicable to 10.4+, 10.3 doesn't seem to allow to create table from a table value constructor.