Apparently bananas as we know them are a mostly sterile hybrid of two other trees.
They self propagate like you say (but humans also spread them around). Bananas have a near zero rate of sexual reproduction, if you can get one to produce a seed, it's viability is low.
If you can get the seed to germinate, the resulting "offspring" from that will be distinct from the original banana, a new variety. It will not necessarily be "true to seed". It might be a better banana, or worse.
If you plant a lettuce seed you will get the same lettuce, year over year. Same with peppers and tomatoes, etc. Their traits were bred instead of cloned.
They self propagate like you say (but humans also spread them around). Bananas have a near zero rate of sexual reproduction, if you can get one to produce a seed, it's viability is low.
If you can get the seed to germinate, the resulting "offspring" from that will be distinct from the original banana, a new variety. It will not necessarily be "true to seed". It might be a better banana, or worse.
If you plant a lettuce seed you will get the same lettuce, year over year. Same with peppers and tomatoes, etc. Their traits were bred instead of cloned.