iPhone dual sims with personal hotspot

I have dual sims activated on my iPhone XS. I also have cellular data switching on. I noticed when I’m using my hotspot with my iPhone and I answer a call on my other line the data switches flawlessly on my iPhone and I can continue to surf the internet while on the call and when I hang up it goes back to the main data carrier. But it doesn’t switch with my hotspot. I don’t lose connection with with the hotspot but there is no internet until I hang up and the phone switches data back. My question is why does the data switch between carriers with no problem but the hotspot doesn’t? And yes i have hotspot on both plans