Giant Template and "special" natural attack reach

[Hulk'Thar]

If a creature has a natural attack with a reach other than its "natural reach" does that attack's reach get modified by the Giant Template and if so, how?

For example, an Otyugh has a "natural reach" of 10 feet which it uses for its bite while its tentacles have a 15 foot reach. If we make it a Giant Otyugh it gains a "natural reach" of 15 feet which it uses for its bite but what is the new reach for its tentacles?

I think they would bump up to 20 feet, following the same progression as "natural reach" does for a Large (tall) base creature (5->10->15->20->30) but I wanted to make certain that was the case since I have seen such attacks advanced in other ways.

[Bizbag]

Are you asking, essentially, if the Otyugh's "extended" reach increases
proportionally, rather than by a flat 5'?

If the rules are explicit somewhere, I haven't seen them. I'd treat the tentacles as a Reach Weapon instead of an exception, so it'd reach out 30'. (You don't progress to Huge (long) first).

This sounds very dangerous, and it is. But also remember that this Otyugh will have only 19 AC and 51 average HP, and it does not have Combat Reflexes. A smart level 5 party can overcome this Otyugh easily if they don't simply fritter around in range of its attacks.