No FDA isn't the most stringent by a long way. The ECG function on the Apple watch 4 only received FDA 'clearance' which is a fast track procedure to allow devices which cannot be used for any real diagnosis to be marketed. FDA 'approval' is a much longer process and that one is tough.
The HSA doesn't even automatically approve devices which have been through the full FDA approval process, although it does take that into account, with just FDA clearance .. doesn't mean much.
It's down to Apple to submit it and HSA to decide if it's a class A device, which should be registered very easily, or a class B one which will require a more thorough process. I hope the feature is approved here but I'm not expecting it soon.
For those who are not familiar with FDA clearance vs approved. Why is clearance instead of approved? The ECG function on Apple Watch is determined to be substantially equivalent to (similar) another legally marketed device (typical ECG devices sold in the market). No approval is required because the Apple Watch won’t be classified as a class III device. I think the Apple Watch is never meant to be a diagnostic device but rather a monitoring devices. [ie. doctor won’t use reading in Apple Watch to say you have heart problem but rather use this as a monitoring tool to monitor patients diagnose with heart problem]. FYI, Apple Watch ECG function will never be a class A device. Maybe a class B or C (HSA classification: https://www.hsa.gov.sg/content/hsa/en/Health_Products_Regulation/Consumer_Information/Consumer_Guides/Medical_Devices.html)
https://www.fda.gov/medicaldevices/resourcesforyou/consumers/default.htm
Extracted from FDA website
What is the difference between Cleared and Approved?
In order for medical devices to be legally marketed (sold) in the United States, they are required to be cleared or approved by the FDA unless it is 510(k) exempt.
Cleared medical devices: These medical devices are ones that FDA has determined to be substantially equivalent to (similar) another legally marketed device. A premarket notification submission is referred to as a 510(k) and must be submitted to FDA to review and provide clearance.
Approved medical devices: Approved medical devices are those devices that the FDA has approved a premarket approval (PMA) application or a Humanitarian Device Exemption (HDE) application. This review and approval process is for Class III medical devices (the ones with the highest risk) and involves a more rigorous review than the 510(k) review process.