If you want "reliable starting in sub-zero temperatures", the test with an ohmmeter isn't considered to be sufficient to ensure that that the plug has an accurate tip temperature.

For 99% of the forum members, the requirement to pull all plugs and test them in a vice for absolute assurance of 100% performance isn't required.

I've never tested a glow plug in a vice. The test with the ohmmeter has worked with 100% precision for the past 10 years.