If you have a Trek Package, yes, a key is included and is delivered during pre-trek.
If you don't have a trek package, you need to select a key separately.
You can add on extras, such as key online here: https://www.treksupport.com.au/add-extras
An example
The below transfer and food drop booking (screenshot from an email booking confirmation) does NOT include a key hire. The person who booked this needs to order a key.
The below trek package booking does include a key.
Keys are not automatically included in food drop orders because customers have the option to order from us or the Visitor Info Centre