Check_urdf does not expand macros in Inertial: mass attribute correctly

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I discovered that for some reason both these packages are unable to parse if any attributes of mass or intertia are specified as xacro:property macros, but parse well if replaced by literals.

This reads as if you are passing xacro to check_urdf and urdf_to_graphviz.

As far as I know those two tools only work with URDF, not xacro. So you'll have to first convert from xacro to urdf, and then pass it on to check_urdf and friends.

which works half decently in Gazebo & fully in RViz & joint_state_publisher

This probably works because whatever launch file loads your robot_description parameter uses something like the following:

<param name="robot_description" command="$(find xacro)/xacro '$(find your_pkg)/some_xacro_file.xacro'" />

that converts xacro to urdf and stores the result on the parameter server in one go.

How can I try to make these macros work well in both Gazebo and the urdf parsers?

That should be clear now.

Which gits should I be raising issues in? I checked some commercial well maintained URDF's (Clearpath Robotics Ridgeback & Gazebo-ROS-demos), both face the exact same issues despite running well in Gazebo & RViz

I don't think there is actually a problem to report.

Please try converting xacro to urdf and see whether that fixes your issue(s).