Weight compared to WFA scale in handicaps is not all that meaningful - read some of Don Scott' books on this.

If the handicapper was fair dinkum she should have got 59kgs minimum.

Explain this,

How could a two-time Cox plate winner only get 2kgs more than a 3yo?
Sunline had 11 group 1 victories prior to the race
Lonhro (who was scratched anyway) had 1.

If the 58kgs was not a joke, then I don't know what is?