Is the prostration of forgetfulness obligatory for an omission that does not invalidate the prayer if done intentionally?

Primary text

The prostration of forgetfulness is not obligatory for an omission whose intentional performance does not invalidate the prayer. Ahmad holds that prostration is only required for matters explicitly narrated from the Prophet, peace be upon him, or matters analogous to them, such as an extra fifth rak'ah, omitting an obligatory part of the Tashahhud, or omitting declarative requirements following the concluding salutation (Taslim).