Is a signed disclosure form the only way to demonstrated compliance with SCS 2.1?

No!  The ACCME does not require that providers utilize a disclosure form to collect the required information.  (Standard of Commercial Support 2.1 states that the provider is required to demonstrated that anyone in a position to control the content of a CME activity has disclosed any relevant financial relationships with commercial interests to the provider.)  A disclosure form is only one of the ways providers may collect disclosure information – they could also collect verbally (and document it in a spreadsheet, table or database), or collect electronically (email, web-based form or database).