English borrowings vs. English words

Here's an interesting sign that we saw recently in the window of a clothing store at a highway rest stop, advertising a really good deal.

Reduced from $300 to $150!

You will notice immediately that there is an English word on this sign. But it may surprise you to know that, in fact, all the words on this sign but one are English. Or, to be more precise, they are of English origin.

The text in green reads:

Orthography: 매쉬 베스트 + 점퍼 SET
Transcription: meswi beseuteu-wa jeompeo seteu
Pronunciation: me-shwee be-suh-tuh-wa juhm-puh setoo [mɛ.sʷi bɛ.sɨ.tʰɨ-wa tʒʌm.pʰʌ sɛ.tʰɨ]
Meaning: "mesh vest and jacket set"

Excluding the plus sign, this line consists entirely of words of English origin:

meswi 매쉬 from mesh
beseuteu 베스트 from vest
jeompeo 점퍼 from jumper (British English meaning 'sweater', but used for 'jacket' in Korean)
seteu SET from set

So why are the first three written in the Korean alphabet, while the last is written in the Roman alphabet?

I don't know why.

First hypothesis: The first three words are Korean words—though Koreans may know they are from English, they function as ordinary Korean words. The fourth word is not a Korean word, but an English word that all Koreans recognize from having studied English in school. This accounts for the difference in orthography.

Second hypothesis: All four words are equally Korean, but the last is written in the Roman alphabet to attract attention and lend cachet.