Why does Rob ter Horst not use equipment at the highest accuracy level for his smartwatch accuracy studies revisited?

Rob ter Horst’s scientific justification to choose the Polar H10 as his reference device is based on the paper: RR interval signal quality of a heart rate monitor and an ECG Holter at rest and during exercise https://pubmed.ncbi.nlm.nih.gov/31004219 of the Swiss Federal Institute of Sports in Magglingen: But according to g.tec medical, they do not …