P/T/K Endings and Tones

Most learners are taught that Cantonese has 6 tones:
high-level, mid-rising, mid-level, low-falling, low-rising, low-level

In Cantonese, any syllables ending in p/t/k will always be a level pitch countour.
high-level: 執笠、不、北
mid-level: 鴨、押、百
low-level: 習、沒、樂

The only exception is one of those syllables undergoing tone change to mid-rising, for example as the second syllable in a word.

When some people count the # of tones, they only account for the pitch contours, so 6 tones in Cantonese. The more Chinese way of thinking of tones is to consider p/t/k syllable endings as a separate tone from those other syllables that have the same pitch contour but do not end in p/t/k.

Since Cantonese only has p/t/k syllables in the 3 level contours, they will say that Cantonese has 9 tones.

However, the main point of this post is that in Hoisanwa – although I still haven’t made much progress – I did notice that the “you plural” syllable is “niak” with a high-falling tone. I wonder how many tones there are in Hoisanwa then, if counting syllables ending in p/t/k as a separate syllable?

And I vaguely remember learning somewhere that syllables ending in p/t/k can only ever be level tones … but I guess that must have been a Cantonese-specific rule?