Looking back to an old thread. Buttons and their settings

While trying to get my confusion sorted I saw this thread:
button icons

I have this flow:

[{"id":"8727ad88.92807","type":"inject","z":"df652827.d02c3","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":2900,"y":1350,"wires":[["4935109b.9280f8"]]},{"id":"4935109b.9280f8","type":"function","z":"df652827.d02c3","name":"Asterix","func":"msg = {icon: '<i class=\"fa fa-asterisk fa-2x\"></i>',fontclr: \"white\"};\nreturn msg;","outputs":1,"noerr":0,"x":3040,"y":1350,"wires":[["5b9de14f.acfab8"]]},{"id":"5b9de14f.acfab8","type":"ui_button","z":"df652827.d02c3","name":"28 June","group":"373c4fb2.a22078","order":7,"width":"3","height":"1","passthru":false,"label":"blah","tooltip":"","color":"{{msg.fontclr}}","bgcolor":"{{msg.colour}}","icon":"{{msg.icon}}","payload":"X","payloadType":"str","topic":"","x":3270,"y":1350,"wires":[[]]},{"id":"373c4fb2.a22078","type":"ui_group","name":"Group 1","tab":"bca4b6a6.5ee09","order":1,"disp":true,"width":6},{"id":"bca4b6a6.5ee09","type":"ui_tab","z":"","name":"Pushbutton","icon":"dashboard","order":44,"disabled":false,"hidden":false}]

The msg.icon is set to the asterisk icon.
and I have some text in the label field.

Screenshot%20from%202019-07-20%2010-50-15

When deployed and I press the inject button, this is what I get:

Screenshot%20from%202019-07-20%2010-49-23

This isn't how I read what should happen in the thread mentioned above.

If I move the {{msg.icon}} to the label field, the correct icon is shown.

Screenshot%20from%202019-07-20%2010-52-52

Screenshot%20from%202019-07-20%2010-53-04