I've had the most luck with OISD as the blocklist; others have the exact problems you describe (in fact all other blocklists I've tested have had frequent issues).
Since changing, I've had maybe 2 sites that didn't play nice with the filtering. These issues are not inherent to network-level blockers, but the configuration of those blockers.
It makes me so uncomfortable to see staff like this justify the use of these monitoring technologies. Employees are increasingly treating their staff like children, and with headlines like this, it seems increasingly appropriate.
This is standard at self-service checkouts in Australia. Both Coles & Woolworths (the 2 main supermarkets) have this imployed. Unrelated to the topic, they also watch what you bag and will lock up and sound an alarm if it think you've added an item without paying.
Absolutely atrocious. But back on-topic, these stores also have cameras in every single aisle, from ever perspective. They absolutely track people throughout each store.
Centrelink is slowly working on this (although glacially). The new earnings system uses Single Touch Payroll info from ATO seamlessly where it's available.
Background data matching is becoming more automated, which should give way to future prefill opportunities.
Given how much money the department spends on processing staff (and how unreliable they are), it's absolutely in their best interests to work on such systems.
You mention myGov, which is interesting. myGov doesn't 'connect' services, and information doesn't pass through myGov; all info is shared between the services directly. myGov is purely a secure portal, nothing more.