The power thing is really hard to get right i've found.
We spent about 2 hours on Sat trying to get the Elite one i got from an STWer correct.
Even now, i'm not convinced it's correct.
Using the settings from Zwift, we were doing side by side testing with my turbo and i was getting 2.1w/kg on his bike/setup and 2.5w/kg on mine, for the same sort of level of effort/cadence.
So it wouldn't be too hard to get it completely the opposite too.
It could be that you're faster/fitter than you thought i guess
I was lucky that the guy i've borrowed my smart turbo from had all his rough figures, along with a power meter to compare to so we know the one i have is pretty damn close to a calibrated power meter.
In some ways, it doesn't matter of course. Sunday morning i was riding the Watopia mountain, a couple of guys ahead and a couple closing, when they got closer i uppped my pace to pull back ahead. It doesn't actually matter if theirs was correct, if mine was correct, or somewhere inbetween, it still gave me the push to get a decent workout
But, if you're sticking out 4.0w/kg and are not already pretty damn fit and fast, then you can bet it's likely your config is wrong... But without knowing you and how you ride, it's impossible to say.
Gauge it off Strava possibly to an extent... work out where you are comparable to other riders etc.
Me, say on a run i know and like locally i'm 56th out of 118 riders on a trail. On a Watopia ride i'm 17403 /42406
Which if you work out is just better than 50% on both i guess. Meaning in the real world i'm probably not a million miles away on both disciplines.
They're only 2 quick examples i pulled out, but the rest is likely quite comparable.