[hnfong]

I suspect the difference is more "academic" than otherwise.

It would be interesting to give a Hong-Konger a test with pairs of characters, one of 1st tone and the other 7th tone, and see whether they can guess which is which.

I suspect with minimal training they'd be able to score significantly better than random chance. (Willing to try it out!)

[ngcc_hk]

No need of test and I knew nothing. But I can be sure we hk Cantonese know and immediately hear if the other speak in canton or Malaysia Cantonese very quickly.