The sole function of magnets in passive pickups is to magnetize the strings. The type of magnet is immaterial, but its strength (Gauss rate) is important. The prime reason why the AlNiCx family of rod magnets is mostly preferred for single coil pickups is their weaker magnetic strength as compared to the ceramic and neodymium types.
There is no sound or tone in magnets/magnetism. However, stronger magnets impart more magnetism to the strings and in turn a stronger signal is induced into the pickup's coil wire. Stronger signals will typically show a different audio signature - more output, more drive, more "push" to an amp's front end, thus more "balls" may be recognized.
FWIW, A3s are about half the Gauss rate of A5s, thus typically producing somewhat lesser an induced signal. However, the beauty of the electric guitar is what it feeds, and at the end of the signal chain is some manner of amplification that can ratchet up a somewhat weaker signal's output that's more clear and focused, and with more headroom than a more "over driven" signal.
Does this mean there's a bit of a "guessing game gamble" with guitar pickups. Yes, to some degree. It is what it is, and it's all good, promise.
