Yes you could do that but I said it should be the service disconnect because it would make little sense to have a disconnect with an OCPD ahead of the panel and not use it as the service disconnect.
OK...here is how this new 2020 section [230.85(3)] is being manipulated to avoid other parts of the Code that may cost the contractor and the property owner $$$...
1. On service upgrades, install your new outside meter/main breaker equipment per 230.85 and label it EMERGENCY DISCONNECT-NOT SERVICE EQUIPMENT per 230.85(3) and you are now permitted to run 3-wire SEU cable into a main breaker panel making this your Service Disconnect-Service Equipment. Now you are permitted to leave old 3-wire branch circuits to your dryer and range.
2. Same thing on generator service rated ATS additions per this thread. Add the ATS outside and label it EMERGENCY DISCONNECT-NOT SERVICE EQUIPMENT per 230.85(3) and you are now permitted to run 3-wire SEU cable into an existing main breaker panel making this your Service Disconnect-Service Equipment. Now you are permitted to leave old 3-wire branch circuits to your dryer and range. No need to separate neutrals and grounds, no need to move your GEC outside to the ATS. You can also avoid installing a Surge Protective Device per 230.67 because you have not technically "replaced the service equipment" per 230.67(D).