I've just updated our test environment to use the latest version and I now get the required information from the Indexer:
[
"height_word_emus" => "526636",
"width_word_emus" => "1511085",
"height_word_inches" => 0.57593613298338,
"width_word_inches" => 1.6525426509186,
"height_word_cms" => 1.4628777777778,
"width_word_cms" => 4.1974583333333,
]
I'm not sure why the previous version wasn't doing the same but I'm glad it is now!