Transferring a Resource Group from a development company to a client company

Precondition: a development company has prototyped a system in an Azure Resource Group (App Service + DB + SendGrid) in their own subscription. That subscription has many resource groups. The client company now wants to take over that one Resource Group. The client company must not get access to the development company subscription. Development company has a login (different id) to the client subscription.

Am I correct in thinking that to transfer the resource group, the only way to do so without actually re-creating the resources is as follows?

Client company creates a new Subscription (B) under its own AD/ownership/whatever you call it.
Client company moves RG from Subscription A to B
Client company switches Directory of Subscription B to Client AD
Client transfers RG from Subscription B to Client's main Subscription (using client login)
Client deletes Subscription.

I just wanted to confirm that this workflow would work and is the only way to do so? (without redeploying resources from scratch).

Solution

I think this is correct (from what I've know and from this article, for example). I didn't hear about any new advances here, so yeah. that is the way to go.

As a side note, you really want your stuff in code, so you don't have to do all that stuff, just apply the code to the clients subscription and you are good.