These people don't know the phonemic alphabet as well as you do, but the explanation is really clear.
https://www.englishclub.com/pronunciation/linking-3.htm
Linking Vowel to Vowel
When one word ends with a vowel sound and the next word begins with a vowel sound, we link the words with a sort of W or Y sound.
If our lips are round at the end of the first word, we insert a W sound:
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| We write it like this: | too often | who is | so I | do all |
| We say it like this: | tooWoften | whoWis | soWI | doWall |
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If our lips are wide at the end of the first word, we insert a Y sound:
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| We write it like this: | Kay is | I am | the end | she asked |
| We say it like this: | KayYis | IYam | theYend | sheYasked |
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