adding a prototype in +pckg/Myclass.m for report_pi helps, but shouldn't be necessary I guess:

classdef Myclass
   methods (Static)
      output = staticFunc1(arg1,arg2)
   end
   methods
     val = report_pi(obj)
   end
end

The discussion in https://savannah.gnu.org/bugs/?45444 is on functions in a private subdir. But that is not necessary with classdefs where you can declare the prototype of the private functions in a method (Access = private) block, as per https://nl.mathworks.com/help/matlab/matlab_oop/methods-in-separate-files.html

I don't think any of the patches and tests proposed there by amro made it to the mercurial repository.

consider the hierarchy below with the same functions and methods and definition for Myclass and pckg.Myclass.

./@Myclass/report_pi.m
./@Myclass/Myclass.m
./@Myclass/staticFunc1.m
./+pckg/@Myclass/report_pi.m
./+pckg/@Myclass/Myclass.m
./+pckg/@Myclass/staticFunc1.m
./test_Myclass.m

Executing test_Myclass.m with octave (stable and dev) gives this error message

ver = 4.4.1
hg_id = 7a7c31b93216+
ans =  3
ans =  3.1416
ans =  3
error: subsref: unknown method or property: report_pi

the report_pi method is not found in package +pckg.
Remarkably the static function is found in both cases.
The function definitions are below:

function val = report_pi(obj)
  val = pi;
end

function output = staticFunc1(arg1,arg2)
  output = arg1 + arg2;
end

classdef Myclass
   methods (Static)
      output = staticFunc1(arg1,arg2)
   end
end

% save script as test_Myclass.m
ver = version
hg_id = __octave_config_info__.hg_id
a = Myclass;
a.staticFunc1(1,2)
a.report_pi

b = pckg.Myclass;
b.staticFunc1(1,2)
b.report_pi