I don't think there's any question about that. Perhaps it's just a personal definition. I don't consider amassing a sizeable quantity of stuff you use collection. It's when you begin filling gaps, picking things up for their rarity alone, collection functional things that you rarely, if ever, use....nothing wrong with any of that, of course, just not my thing.
I can recognize the stages I have gone through in acquiring recorded music.
1. Acquire one recording of a work/performance so that I can listen to it and learn it.
2. Explore other recordings for music I really like. For some classical music, it has been a search for the performance that seems exactly as I think the music should be played (and the first one I acquired seemed lacking in some way.) Brahms symphonies were that way for me for a long time. For other works, I really, really like a recording I already have (such as the Fleischer / Szell Brahms PC no. 1) but I try other performances in hopes that I'll find something with a different approach that adds to my enjoyment of that piece of music.
3. Buy the latest, best remastering of a performance I love. For classical music, this is often a worthwhile improvement. I only buy re-masterings for the performances I really treasure.
4. Buy all recordings of really favorite music that anyone mentions favorably.
Now this is collector behavior. Of course, until you have heard a performance, you don't know what you are missing.
5. Buy almost everything that favorite performers recorded (but just for music I like). Szell, Reiner, Walter, Monteux, Casals and Sandor Vegh are in that category for me. For Boradway shows, John McGlinn is in that category.
6. Buy first recordings of music I have not previously been interested in. I'm still filling out my library of chamber music.
7. Read a mention of music unknown to me that sounds interesting and buy it.
Music on CDs can be cheap enough to make this process almost guilt-free. If it costs less than $ 10 with tax and shipping, I buy the recording. More than that, I'm resistant. Perhaps, I'm a responsible collector.
Bill