As far as I know, they are not multi-trunked palms. It was probably 3 separate palms planted closely together.

I had a multi trunked windmill from lowes. The second trunk was shorter than the main. But when the winter of 2010 killed the main trunk I had to remove it. It was obvious that they were 2 separate seeds.

I've seen them planted in pots in twos and threes at garden centers. They don't do have pups like Med fans or needles. They looks best when the trio is consisted of three different sized palms.

Sometimes you see them planted as triples, they dont naturally pup like European fan palms, but they can grow in doubles, triples, and occasionally quadruples! I had a double trachy, but the larger of the 2 palms died for no reason in the middle of the summer. The smaller one lived and is still growing today 4 years later.
-Alex

Nurseries often do multiple seed plantings of single stemmed palms in pots. They often do it with multistemmed palms as well just to get that jungly look a lot faster.