You are correct. You can find the police operating guidelines online and they specify that travel to the EU/EEA should be logged on SISII (Schengen Information System) by way of an Article 36.2 alert for all ViSOR nominals (the database that records violent and sex offenders). This is for a discreet check (hence the questions at the border). There is no risk assessment by the PPU - alerts are issued for all travel.

For travel outside the EU, the police guidelines refer to undertaking a risk assessment and making a proportionate decision whether to issue an Interpol green notice. I would assume from your comments that you were assessed as low risk and therefore no need for a green notice (the other explanation is that a green notice was issued but no picked up by the recipient country systems - while that could be the case for Thailand, Kenya and maybe Mexico, its highly unlikely for Canada).

Of course every PPU is different and some officers are more 'jobsworth' than others.  It's a bigger deal to issue the green notice - more forms, more internal approvals etc.

In talking to my PPU about specific countries, they were definitely relaxed about places where they know you aren't asked about convictions and/or it is not a barrier to entry.  I got the feeling that they might be a bit more circumspect if they were familiar with immigration policy for a country and therefore knew you would be making a false declaration. Catch 22 for the risk assessment - you're meant to be low risk and committed to rehabilitation but prepared to bend the rules when it suits!

If there is an RSO who has been to the US while notifying, then we will know that there truly isn't any backdoor/underhand data sharing going on!