Change to employer 401(k) plan added “Roth In-Plan Conversion”. Does this mean I can do a MBDR?

Listed under the plan changes: “A Roth In-Plan Conversion allows you to convert pretax contributions and investment earnings into a designated Roth account under your plan. The amount you convert is taxable income to you in the year of the conversion and you will be provided a Form 1099-R to include with your personal income tax return. After conversion, those contributions and earnings assume all the characteristics of Roth contributions” Does this mean I can do a MBDR? Within account, it appears I can still only contribute Pre-tax or Roth to my 401(k), there is no after-tax option. Do I need to be able to BOTH contribute after-tax dollars and have the ability to do an in-plan conversion? In the Summary Plan Description of the account, under a section titled “After-Tax Contributions”, it reads “Previously, the Plan allowed participants to make after-tax contributions…” (then proceeds to explain how to handle previous after-tax contributions which is irrelevant here) Regardless of whether or not this allows me to do a MBDR, what are the benefits of a Roth In-Plan conversion? Thanks!