In the US & AU, I know they use a Theoretical Hold Worksheet which pre-specifies the win/lose ratios and is required for every machine. That worksheet doesn't make use of past wins/loses, i.e. it is stateless. This matches what you say.

However, I do not know what the situation is in the UK/EU at present, and I do not know what it was 20 years ago (when my brother was working there).