It does appear to be true that conjugal apps tend to get more scrutiny, and perhaps even more only a few years ago. Which one might assume to be related to same-sex relationships, but my impression is that even more conjugal apps are actually due to inability to get divorced - esp Philippines (but warning, I don't have any data, just an impression from this forum). And given that the conjugal requires no common law (mostly time) commitment or legal commitment (marriage), it makes determining whether it's a 'real' relationship harder.
That said, I'm a little surprised at the refusal on TRV grounds, but I'm also perhaps forgetting from four years ago. In short, it seems now that IRCC is a little less strict/ideological about the TRV issue. (Although not entirely consistent about it, so hard to say). That said, age difference (and related factors I don't know about) may have been more decisive.
I think it's too bad you didn't appeal back then, or apply right away after getting a TRV refusal.
All that said: I think you've far better chances of it going smoothly this time. I'd just stick to your guns and methodically lay out the extent of the relationship and time you've spent together. Lack of ability/attempt to become common law may come up - rebutted simply enough by "I have a life in Canada (and conjugal exists to allow couples in this situation to do so WITHOUT giving up that life in order to qualify for common law).
Last comment/question: I gather from your above that you were not present for the interview? Have you been given the option to do so? I don't know the rules about this - but I would push for you to be allowed to be present (whether online or physically).
Again, good luck.