The following script tested in 2.29.1 and earlier versions:

class foo {}
funcdef void bar(array<foo>);

results in following errors:

array (0, 0) : ERR : The subtype has no default factory
filename.as (2, 24) : ERR : Can't instantiate template 'array' with subtype 'foo'

These errors occur for every funcdef declaration that contains an array with a script-declared class subtype either as a parameter or a return value. Contents of the class don't matter, including whether the class contains an explicitly stated default constructor or not. The error information is certainly incorrect as this kind of an array can be instantiated anywhere outside of the funcdef declaration.