Because if you're using satchels, unless they're platinum you don't have Paypal seller protection.

So not true 😉

If you use the same Aust Post lodgement slip that you use for registered post, delete platinum from express post tick box, attach tracking number sticky label  and have stamped by post office at lodgement - voila ... no problems, more than satisfies Paypal requirements.

I have done this for 5kg prepaid satchel too.