i googled this; looks like it means "Interactive Voice Response" menu, describing automated phone systems where the user navigates a series of options using either their phone buttons or their voice.
That's what they are called in India, at least, where I live, and where I am from, although the term would not have originated in India, since it would have been brought in by mobile phone companies.
Although I have a good amount of exposure to, and familiarity, with US terms and slang, due to older relatives up to grandfather level having visited the US for more than short periods, having visited the US myself, and having worked in US-based companies (but in India), the exposure is not complete, that's why I was not familiar with the term phone tree.
I've worked at call centers and contact centers whatever the hell you wanna call them places for 15+ years. have you legit never heard the term phone tree before? I'm on the east coast in case its a regional thing, that's like literally what my dad who wasn't an uneducated person called them. totally just curious here!
i Googled that term
looks like it's another name for an IVR menu.