Does anyone's iPhone sounds muddy/narrow sound stage using earbuds/headphones?

I've noticed this issue back in 2015 when I was still using my iPhone 6s and 7th gen iPod nano. I very often used my nano to listen to music, but one night I was commuting home from work and didn't have my iPod nano with me so I used my iPhone 6s to listen to the same playlist. The tracks were either bought from iTunes or streamed on Apple Music. For some reason I thought it sounded strange on my iPhone. The only way I could describe it at the time is it sounded compressed as I didn't have that much knowledge about audio quality as I do now, but I'm not an audiophile. When I got home, I grabbed my iPod and plugged the same EarPods and played a couple of tracks jumping back and forth the iPhone and the iPod to hear their differences.

I've kept this practice after getting my first paid of Bluetooth earbuds and upgrading to the iPhone X. Strangely enough the iPhone X sounded like the 6s. I lost my iPod nano while partying, but I was giften an Apple Watch series 3 and I immediately set it up and loaded my playlists onto it and listened to it as it was my first Apple Watch and was excited to see what it can do. To my surprise it sounded a like my iPod, cleaner, more detail, and has a wider sound stage. I then borrowed my mom and my step dad's iPhone X to see if they have the same thing happening, and to my surprise they sounded the same as my iPhones.

Fast-forward to today, I now have an iPhone 13 Pro, an Apple Watch series 6, a Vivo Y85A (with Apple Music installed) and I can tell you the iPhone's audio quality still sounds pretty bad in comparison. I would always opt to listen on my Apple Watch as it delivered better sound quality, and would only use my iPhone to edit my playlists.

Over the years, I have owned and tested several earpods and headphones:

• Polaroid Wireless Earbuds (owned)
• Apple AirPods 1st gen (tested)
• BeatsX (owned)
• Bose SoundSports (tested)
• Bose QuietComfort 45 (tested)
• Sony WH-1000XM4 (tested)
• Fiil CARAT (owned)
• Fiil IICON (owned)
• Fiil ACTIVE (owned)
• Fiil CC2 (owned)
• Bang & Olufsen EQ (owned)

With that, I can clearly say that the iPhone's audio quality, regardless of the model, sounds a bit muddy and compressed in comparison with the iPod and the Apple Watch.

Has anyone experienced the same? I would like to shine more light onto this issue and hope it gets attention. I feel like a phone that costs as much should have audio quality as good, if not better, as other Apple products.

Eugene