If they don’t show any Dyno runs or data to support their claims, then it might as well be written by a high schooler. Besides, I never trust such blog-sites or magazines; much better to actually read scientific papers published on the subject. If you have any of those, please be my guest and post them here.
I say delusional because what you’re saying doesn’t make any sense. I don’t know what’s wrong with your car, but regardless the issue is probably that the 1200cc engine is not specifically made for this size of car. That’s why it feels underpowered. 89 hp means nothing if all that power is produced up top. You need torque for city-driving, and that torque can only be provided by a bigger engine(or by turbocharging).
A manual Corolla doesn’t compare, because like I said, you can clutch-dump it at whatever rpm you like to increase wheel hp/tq. It seems like you aren’t even reading what I’ve written above. Neither have you read the link you posted yourself. Context is important, they specifically mention that min losses only occur in direct drive(which is not 1st or 2nd gear), which you don’t mention in your post whatsoever.
