Great question! Wow, you actually made me think on this one, especially on how Siri has changed over the years.
Siri, and I think most all AI, and chatbot responses, are utilizing more natural language when reading things back. So instead of reading each digit like "one, two, three, four, five," it might say something like "twelve thirty-four" or "forty-fifth," because it’s trying to sound more conversational.
Most of the places I’ve lived, I guess I haven’t noticed it because luckily it’s only a few digits. But when visiting relatives in other states, man, I can see how this would be annoying. The digit length sure can get up there!
Unfortunately, there isn’t a setting to switch it back to the old way
If it drives you insane, or if there are a few addresses in your contacts where the address number seems infinite, you could put spaces between the numbers to get Siri to say them one by one. But that seems more effort than what it’s worth.
Here’s a link to submit feedback: Apple iPhone Feedback