Are all non-name words ending with
ize always semantically interpreted as verbs in the English language?
Update: I just found a few: maize, prize that aren't. One about checking for two or more syllables before the ize? Is that a reliant method?
OED notes that -ize is a productive suffix forming verbs. However a word like prize doesn't have an -ize suffix. As you have found yourself, the answer is obviously "No." Words ending -ize are not always verbs.
The OED entry for -ize has...
Words that have come down from Greek, or have been at some time adopted from Greek, or formed on Greek elements.
a. With the trans. sense of ‘make or conform to, or treat in the way of, the thing expressed by the derivation’, as baptize (prob. the earliest -ize word in English), anathematize, anatomize, ...
Baptize (which is properly spelled -ize even in British English, because it's derived from Greek βαπτίζειν with a zeta ζ ) is first attested in OED in 1297. The entry for -ize itself has a meta-citation from 1594, indicating that the suffix had become productive by that time. It's interesting that Nash calls such words "Italianate" rather than Greek.
1594 T. Nashe Christs Teares (new ed.) To Rdr. sig. **ijv, Reprehenders, that complain of my boystrous compound wordes, and ending my Italionate coyned verbes all in ize.
Prize, which is obviously not formed with -ize as a productive suffix, is found in late Middle English and first attested in that form in 1467, although a form pris is cited from 1250.
I put forward that there is no way of definitively finding words with a verbing -ize suffix other than by individual examination. That is, even identifying disyllabic words ending in an -ize syllable may not be sufficient. A single example is enough to prove that: assize n. OED contains 39 examples of nouns ending -ize, most of which are obsolete; however supersize (from 1876) is just about still current. But that example means that even more than one syllable before -ize is not reliable.