Triliterals in strange places

In a grammar I was looking at lately, I came across the following sentences:

"Nouns may be verbalized, or verbs nominalized, simply by bringing the stem into a suitable rhythmic form... Most of the rhythmic patterns call for a tri-consonantal stem. If a stem is di-consonantal in its primary form, a consonant (usually the glottal stop) is added to give it the proper structure... Often in the course of forming derivatives, stems that are too long are forced into one or the other of the regular patterns. They are cut down by the loss of quantity or of vowels or consonants as may be necessary."

Was this a Semitic language, or perhaps some less well known Afro-Asiatic cousin? No: this was Sierra Miwok, the pre-conquest language spoken by the Native Americans of central California inland from the Bay. (See map.) The "rhythmic patterns" only involve changes in quantity and CV>VC metathesis, not insertion of specific vowels as in Semitic, but the parallel is striking. Here are a few examples:

leppa- "to finish", with a CVCVCC pattern imposed, becomes lepa''- (gaining a glottal stop).
ṯolookošu- "three", with a CVCCV pattern imposed, becomes ṯolko- (losing the š).

Compare Arabic:
'ab- "father", with a 'aCCaaC plural template imposed, becomes 'aabaa'- "fathers", gaining a glottal stop (historically a semivowel, but never mind that)
`ankabuut- "spider", with a CaCaaCiC plural template imposed, becomes `anaakib- "spiders", losing the t.

Reference:
Freeland, L. S. 1951. Language of the Sierra Miwok. Baltimore: Waverley Press.