Done already, now it's your onus to prove me wrong, which you haven't & can't.
Get the weekend started!
Ok so you have shown us two speed tests with no mention of the actual connection speed to your ISP. Additionally you have shown us no bitrates or anything from the actual devices in questions, it's all a bit of guess work.
Here are some figures from an Apple 4K TV to compare both WiFi and Ethernet including Mulan for
@dan~ which demonstrates certainly on an Apple TV 4K that Disney+ runs at full 4K at around 16.5Mbps.
The Apple TV in question is normally wired to a Gigabit Ethernet Switch running at full speed. A speedtest running from the native App gives this speed. That's about as fast as Gigabit LAN will get.
Ok so now I have connected to WiFi, where the Apple TV is located is in the middle of a metal rack so doesn't get great WiFi connection. Actual report connected speed is a mere 72Mbps so pretty crap really.
Results are pretty poor
As you can see download speed is pretty rubbish, I thought I would even have to move but thought I would try and see what the results looked like anyway. You can see that the upload was a bit quicker and I have a reasonably busy WiFi network with 20 odd devices currently connected.
Since the OP asked about Mulan (not sure if the Cartoon or the newer one) but both are available on Disney+ in full 4K and here is the bit rates as reported by Apple TV.
Wired:
So as you can see the network bandwidth (which is the peak throughput is higher) but average bitrate is around 16.4Mbps and is running at 4K.
WiFi:
Network bandwidth is lower as expected because it's a rubbish connection. Average bitrate was slightly higher at 16.77Mbps.
Indicated bitrate is identical in both as it's playing the exact same stream i.e. the max quality available and so Picture Quality is identical.
Long Way Up Apple TV Original
Wired:
WiFi:
Same indicated bitrate identical PQ
Netflix "Is it cake?"
Wired:
WiFi:
So in summary the indicated peak and average bitrates are identical even on this pretty crap WiFi connection. The average bitrate which is measured in realtime and is constantly altering is in pretty much the same. Typically on Netflix when the quality does drop down it for example drops to around 11Mbps.
To be clear no one is arguing that wired is not a better connection and ultimately allows more speed. However for streaming so long as you can sustain a reasonable WiFi connection then there will be no differences in the bitrate of the stream and since it is playing an identical file stream no differences in PQ.
If you are seeing otherwise suggest you look at actually getting some decent stats off the your equipment to check you don't have a fault somewhere.
And to
@dan~ yes it would appear Disney is in 4K+