It's the same for the last string. Doesn't end with an end byte. The script ends when it hits an end byte value, which in this case passes beyond this script block, the monster names and spells. The monster and spell names are fixed strings, though.
The last string is supposed to end at $270862 but ends at $272962. The whole block, with the available space included, is between $270200 and $270AFF, so the extraction gets quite far before it hits the end.
This is the only block in the game that has this kind of format, so fortunately, it's not a real biggie. But maybe this applies to other games besides this and RS2.