Coverage of Bariatric Surgery under new IRDAI rules October 2020

These are two different things. The 1-October guidelines are exclusions, wordings standardized, they have nothing to do with underwriting (risk selection) by an Insurance company.
For instance, a policy can cover pre-existing disease like a Cancer from Year 4, but that does not change how insurers select and offer or not offer or charge premiums to people with a history of Cancer. Hope this clarifies.

The wordings, standardization will impact people with insurance policies - existing & new - claims which were earlier not payable for Obesity, Mental Illness (as per the t&c) will now be payable.