My friend and I are both native speakers of Australian English.
He thinks "one" and "won" sound different and feels "a one-liner" sounds wrong and should be "an one-liner". He does think the two words rhyme, which would indicate they have the same vowel but only "won" begins with a consonant sound, to his ears.
("Won" here is the past-tense of "win", not the currency of Korea.)
So does my friend have a point, or is his thinking affected by spelling, or does it depend on region or speaker after all?
I grew up in Melbourne and he grew up in Brisbane. Australia is well known to lack regional accents though. We both grew up among what linguists call "Broad Australian" speakers, but we are both speakers of "General Australian".
I have always taken an interest in linguistics and my friend has not. I have travelled the world a lot. My accent has changed, and I'm not currently in Australia to go out and listen to people.