Unlikely.
It sounds like made up nonsense.
8 hours, 10 hours, 12 hours it will be all be guesswork with little or no evidence to back it up.
capitalpath.com.au say this:
No appointment is necessary for this test Your Doctor has referred you to have a ‘fasting’ blood test. To ensure reliable and accurate test results, it is important that you follow these instructions carefully. Please ensure that you have nothing to eat or drink (you may drink water) for 8-12 hours prior to presenting for the test. It is recommended that you fast for 8 hours for a ‘Fasting glucose’ and 10-12 hours for ‘cholesterol/lipid’ testing.
Do not fast for any longer than 12 hours, as this may affect your test.
Ensure that you drink plenty of water to stay well hydrated. Smoking should be avoided. Continue to take any prescribed medications, unless advised otherwise by your doctor. Early morning appointments are available at most of our Collection Centres. Please phone your most convenient Collection Centre to make an appointment. For further information on the blood test procedure please see the Patient Information Sheet titled “What To Expect From My Blood Test”.