I’ve seen it do that for decades now, and in at least two cases I see it happen is when a highway enters town and gains a name, like how Florida Route 92 becomes International Speedway Boulevard when you enter Daytona Beach. Or, when another route joins the corridor you’re on, like throughout North Carolina US-1, US-15 and US-501 weave in and out of each other a few times along with a few state routes joining and leaving.
So I think when it hits points like this, it sometimes interprets them as intersections rather than junctions, and its programming requires it to issue a direction for an intersection. YOU might not see it as an intersection but IT does.
A bigger problem I have than occasionally hearing “Keep straight on Highway 20” is “Keep straight on US-20, US-94, US-1, US-15, US-501, US-99, US-98, NC-24, NC-27, NC-17, PG-13, PS-5, N-64, I-95, I-85, I-40, Bragg Boulevard for 1.3 miles.”
It puts the instruction at the beginning, and then it talks so long you forgot what it told you to do. It’s how you stack overflow a human.