I have an incredibly hard time getting iPhone’s voice to text to work well in Japanese. So either my pronunciation is terrible, or it’s just not that good. For example, I tried to say 奮う, and no matter what it thought I was saying フル. I definitely extended the う sound long enough, and I tried with a few different pitch accents (since I don’t know the correct one). Yet every time it came back with フル. When I click the word to see what alternatives it thinks I might have meant I get フルール, Hulu, 古, and ふるー. I guess the last one is right-ish, but it’s still weird since there are a few kanji-based words spelled ふるう.
I’ve had this experience with so many words that I’ve all but given up on using voice to text for Japanese. That’s why I had to find out of it’s just not that good or if it’s a problem on my end. Perhaps it’s only this bad why you try to say a single word, which happens to be my use case right now.