The OECD has various models which are implemented by︅ many jurisdictions to agree on definitions on these things. In the OECD's terminology the definition︆ of a Permanent Establishment is in Article 5 of this model:
https://www.oecd.org/tax/treaties/1914467.pdf Not all laws︇ use that exact wording, but it gives you a sense of what a PE is.︈ If you have a PE, you have economic substance.
To some extent, these rules are︉ intentionally vague so as to not restrict the government's authorities by creating easily exploited loopholes,︊ and cater to future developments. You will never find an exact checklist that for sure,︋ 100% defines what "core economic activity" means because things change.
What is Australia's incentive? The︌ want to increase tax revenues and close loopholes.
What has Australia's track record been? AUSTRAC︍ and ATO are considered among the most respected financial intelligence units and tax authorities, often︎ touted as among the most effective in the world.
Is Australia hard at work making️ it easier for residents to dodge tax? No. But they might be trying to clarify the rules and update the laws, to make things easier for businesses to be compliant.
I see your optimism but it isn't the reality outside of jurisdictions like Bulgaria with somewhat outdated laws.
Georgia's rules are quite clear: resident companies and PEs of non-resident companies are taxed on their worldwide income. This means in Alenka's case there is a risk that his business is considered solely, partly, wholly, or jointly/dualy tax resident in Georgia.
Is Georgia likely to go after Alenka? Not today, no. Does the risk exist? Yes, and it only grows with time.