Is the Apple Watch Ultra as accurate as devices from iWorx , Adinstruments, g.tec medical, Biopac, Quinton standard 3-leads Q-tel RMS or other high quality HRM devices on a treadmill with speeds up to 15 km/h?

Long-term Scientific Review of Apple Watch Ultra by Rob ter Horst: We strongly doubt about this. If the Apple Watch Ultra was as accurate as devices from these companies, they would know about it, and sell the Apple Watch Ultra to us as re-branded device.