that's not how it works.
if the source is low quality, all converted files are also going to be low quality.
usually in this sort of circumstance the sound would even be worse because the audible irregularities(pop, hiss, etc) and the missing sound bytes from the original low quality conversion would be even more pronounced.
I just asked chatgtp:
No, you cannot upload a song to iTunes in low quality and then download it at a higher quality. When you upload a song to iTunes, the quality of the file is determined by the original file you upload. If you upload a low-quality file, it will remain low quality on iTunes.
However, if you are an Apple Music or iTunes Match subscriber, Apple may replace your uploaded song with a higher-quality version from its library, but this is dependent on Apple having the song in its library and the quality available there. But downloading it again from your library would still reflect the original quality of the uploaded file unless it was matched and replaced by Apple's higher-quality version.
Then I asked how many songs Apple Music has in its library:
As of the latest information available in 2024, Apple Music has over
100 million songs in its library. This makes it one of the largest music streaming services in terms of the number of tracks available to subscribers.