Why is 灸 pronounced jiu1?

Question

The pinyin of 灸 as in 针灸 (acupuncture) or 艾灸 (moxibustion) is clearly given as jiu3, as shown in, among others, MDGB and Zdic.

The single character doesn't even have alternate pronunciations, only jiu3 is listed.

However in speech I've always heard it pronounced jiu1 (example: https://youtu.be/RJFsJi7JvFI?t=10). In this other video though (https://www.youtube.com/watch?v=9lJhs4vz4eI) it's pronounced as the dictionary suggests.

Is jiu1 a pronunciation of southern dialects? How did it come about?

Yes, it is a common mistake. Most of the people around me make the same mistake. I realized it is wrong just a year ago, and I live on the north bank of the Yantze River. — T-Pioneer, Commented Feb 19, 2021 at 12:25
Both 普通话 (Mainland) and 國語 (Taiwan) standards for Mandarin have jiǔ, corresponding to Middle Chinese 上聲. However, most southern Chinese topolects have readings with tones corresponding to Middle Chinese 去聲, e.g. Cantonese gau3, Hokkien kiù (文) & kù (白). Both readings exist in Guangyun. — Michaelyus, Commented Feb 19, 2021 at 15:01

Mou某 · Accepted Answer · 2021-02-19 13:40:20Z

This is not an answer but some references that might be helpful and are too long for the comments section.

This is clearly a phenomenon because the first note written on 灸 in《规范》says:

注意㊀不读jiū。

But, without much of an explanation it is hard to see why they mention it other than the obvious idea that it often gets mispronounced this way.

As for southern dialects《现代汉语方言音库 • 成都话音档》has the following entry:

灸
tɕiəu⁵⁵

The tone is noted as:

⁵⁵

Which is clearly 阴平, the same as jiu1.

Looking through the tones on: 灸 | Wiktionary we also have:

A high flat tone:

Hakka = /ki̯u⁵⁵/

and a middle flat tone:

Cantonese = /kɐu̯³³/

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