In a recent AP article about a hotdog eating contest is the following sentence.
Thousands gathered at Coney Island on the Fourth of July to watch the glutinous gladiators compete in the annual event.
There are a few possible explanations.
The first vowel in gluttonous isn't the same as in glutinous. The former is pronounced with the 'strut' vowel and the latter with the 'boot' vowel (AmE) or the 'you' glide+vowel (BrE).
In deliberately slow speech I would expect 3 vowels in the pronunciation of each word. In the first (gluttonous) they are all likely be the same sound: ʌ. In the latter (glutinous) they are likely 3 distinct vowels: u, ɪ and ʌ.
Normal speech reduces vowels and the last vowel in each word is probably closer to ə. In AmE the second syllable of both words loses a vowel. In place of the vowel is a syllabic 'n' which radically neutralizes any difference between ʌ and ɪ. The typical AmE pronunciations are ɡlʌʔn̩əs and ɡluʔn̩əs. A writer who has heard gluttonous but doesn't know how to spell it is easily going to accept <tin> as the orthographic representation of -ʔn̩-.
And tho I would expect a double <t> after the 'strut' vowel it's not unheard of to have a single consonant. In one-syllable words it's especially common: but cut gut hut &c. In multisyllabic words it's less common. Especially in a stressed syllable. A long time ago a single consonant belonged to the following syllable (as an onset) which left the vowel in the stressed syllable open. Vowels that were in those open syllables now sound like what our elementary school teachers call 'long' vowels or sometimes the tense vowels in bee or boo. So the <u> in glutinous (representing BrE ju diphthong/ AmE tense u) makes sense before a single vowel. But that's not much help when the writer or reader doesn't realize that <glutinous> is not an adjective meaning 'characterised by or given to overindulgence -- especially in food.'