Unsupported Khmer Unicode Language but other apps like Pixelmator or ProCreate…supports by default

I'm from Cambodia and Khmer is my language. I am a graphic designer and most of the works I am working on is Khmer. We are using Khmer Unicode as our keyboard layout. I was so excited to use Khmer on illustrator for iPad but I am so disappointed to see that the illustrator for iPad doesn't support Khmer Unicode but surprisingly Photoshop for iPad does. Why doesn't both support the same features as they come from the same company. I have used Affinity photo and designer too but they also don't support Khmer Unicode on both desktop apps and iPad apps. Illustrator and photoshop both supports Khmer language and I was so excited to use illustrator on my iPad to work on some Khmer text but, again, I reached the same disappointment.