The apostrophe here most likely represents a glottal stop (as in Hawai'i).

In Finnish, the apostrophe marks a syllable break between instances of the same vowel, and sounds like a very short pause. Maybe they use Finnish spelling rules on this planet.

Example word: vaa'an — genetive of "vaaka" = "scale"

Ooh this is fun trivia - originally dragons had a hard time with human names, so it became a tradition for dragon riders (particularly males) to adopt the dragon’s pronunciation as an honorific. So “Simon” becomes “S’mon.”

You say it with a bit of a slur - suhMON or fuhLAX - where the first syllable is not only unemphasized but uttered as quickly as possible then slurred into the next. F’lar really is just “fuhLAR”

IIRC, dragonriders always elide part of their name, and indicate the gap with an apostrophe. It's consistent and explained in the text at some point.