It looks like you're noticing that the data stream rates for Tidal's Pro Plus plan show higher resolution (FLAC 2000+ kbps at 24-bit/192kHz) compared to Amazon HD Ultra, which maxes out at around 900 kbps at 16-bit/44.1kHz. The key difference here is in the streaming quality and the formats each service offers.
Tidal, with its "HiFi" and "Master" tiers, supports high-resolution formats like FLAC up to 24-bit/192kHz, which is why you’re seeing those higher bitrates. They also offer MQA (Master Quality Authenticated) for their "Master" tracks, which can further enhance the sound quality at higher bitrates.
Amazon HD Ultra, while offering lossless streaming in FLAC format, tends to stick to a more standard resolution of 16-bit/44.1kHz for many of its tracks, though it does offer some 24-bit audio, just not as widely available at the higher resolutions like Tidal’s Master tracks. The 900 kbps you're seeing on Amazon HD is likely for the standard lossless 16-bit/44.1kHz FLAC tracks.
If you're looking for the highest possible resolution and streaming quality, Tidal's Pro Plus plan definitely provides a more premium experience in that regard.
By the way, if you still want to enjoy Amazon Music, you can seek help from third-party tools like AudFree Amazon Music Converter to get high quality.