Sure, if you want a guaranteed uncanny valley experience. There is no way a few seconds are enough to cover all the ways a specific person pronounces things. A person's voice is much more than just the pitch and with a 3 second sample anyone who knows them will be able to tell something's off within 3 seconds.
The accuracy or realism of the emulated voice probably depends on how "rich" the recorded material is within those 3 seconds? I mean, if it includes a single long syllable, or some phrase that contains a variety of vowels and consonants.
Apple's announced voice imitation feature requires a 15 minute sample if I remember correctly, and you can bet it would be shorter if they were satisfied with the results.
> if in that 3 seconds it hears you say y'all
I can guarantee that no 3 seconds of text of your choosing will ever be enough to reliably differentiate between all existing dialects and accents, let alone differences between individual people.
There's a reason all the decent fake voice clips on the web are based on public figures with hours of training material - and even with those you can tell within seconds that it's fake, even if you don't know how you noticed it.
Salesmen and scammers have many techniques to get people to act against their better judgement. Urgency is one: imagine a late night voice call seemingly from a loved one saying "I'm stranded, my battery is about to die. Please send the money now -" accompanied by loud environmental noises to mask any artifacts
Unfortunately the targets of these scammers is usually senile old people. I'm incredibly worried about my parents, especially my bleeding heart mother.