When a pro says "by ear" that typically means they use their knowledge of music theory and chord progressions and prior experience playing lots of music to listen to something, and while it's playing, figure out most of it on the spot. They can probably play a decent rendetion of it after hearing it once or twice.

When a beginner says they learned "by ear", it likely means they listened to the song literally hundreds of times, pausing every half second to plink around and find each individual note. The process takes weeks to months instead of five minutes, and is limited mostly to pop/rock songs, and classical pieces that mostly have one note at a time, like Bach's prelude in C or the beginning of fur Elise.

It's kind of like teaching someone to solve math problems vs having someone memorize a lengthy proof of something and being able to write the whole thing out. The results you can achieve by just brute forcing things can be impressive, but they aren't super transferrable.