I believe that error FOCA0006 can also be justified for this test case. The following rules apply to this query, 0.00...01:

XQuery, 3.1 Primary Expressions:

"The value of the numeric literal is determined by casting it to the appropriate type according to the rules for casting from xs:untypedAtomic to a numeric type as specified in Section 17.1.1 Casting from xs:string and xdt:untypedAtomic(FO)"

F&O, 17.1.1 Casting from xs:string and xs:untypedAtomic:

"In casting to xs:decimal or to a type derived from xs:decimal, if the value is not too large or too small but nevertheless cannot be represented accurately with the number of decimal digits available to the implementation, the implementation may round to the nearest representable value or may raise a dynamic error [err:FOCA0006]."