Ashley told me to raise an issue with Chrome team about poor APK performance, when performance on Chrome was OK. Interestingly Chrome team directed me to this discussion posted by the Construct team themselves. This reads to a nivice like me, that there are many people reporting my same issue, and that an engine whic delivers via WebView could be problematic for a considerable number of users, as the disabling of certain instructions on certain GPUs on WebView, is for security reasons and is disables WebGL. That would explain my game running like a dog with 2 legs, but the Google team have stayed my GPU instruction set is fine and not blocked...
bugs.chromium.org/p/chromium/issues/detail