1) Using this https://fedoraproject.org/wiki/Packaging:Guidelines#Requiring_Base_Package as a base, I suggested (not in any bug) to add %{?_isa}  for -libs also in ibus.spec to its maintainer. Following is a part of commit he did. But he also then said this looks unnecessary to him as %{name}%{?_isa} already present.

 %package gtk3
-Summary:    IBus im module for gtk3
-Group:      System Environment/Libraries
-Requires:   %{name}%{?_isa} = %{version}-%{release}
-Requires:   %{name}-libs = %{version}-%{release}
+Summary:        IBus im module for gtk3
+Group:          System Environment/Libraries
+Requires:       %{name}%{?_isa}        = %{version}-%{release}
+Requires:       %{name}-libs%{?_isa}   = %{version}-%{release}