@hongminhee Maybe a regional thing?

https://en.wikipedia.org/wiki/H

> Its name in English is aitch (pronounced /eɪtʃ/, plural aitches), or regionally haitch /heɪtʃ/.

> The perceived name of the letter affects the choice of indefinite article before initialisms beginning with H: for example "an H-bomb" or "a H-bomb". The pronunciation /heɪtʃ/ may be a hypercorrection formed by analogy with the names of the other letters of the alphabet, most of which include the sound they represent.