Bluetooth sound quality: iPhone 6s Plus vs iPad Pro 10.5”

Hi there

So this question is purely out of interest in case my mind is just making this all up. Basically, I‘ve been using an iPhone 6s Plus for three years, and listen to music with BeoPlay H9 headphones (Bluetooth 4.2, AAC, aptX LL (I know iOS devices do not support this codec)). At the end of last year I bought an iPad Pro 10.5” — first iPad I’ve ever owned. After listening to music using both devices (same headphones) I noticed that to me the music sounds more full and less muffled (or maybe, less compressed) when my headphones are paired with the iPad Pro. It is a slight difference; I am perfectly fine using either my phone or my iPad, but definitely the high end of the frequencies are more pronounced, and it seems an overall more balanced, (higher quality?) sound on the iPad.

So am I imagining this, or does anyone know if Apple have improved Bluetooth hardware/connectivity in their newer devices? I use Apple Music in both cases.