Enable Send to Stripe Condition not giving option to use 'User Defined Price'

The ‘Enable Send to Stripe’ Stripe Condition does not pick up GF Produce Pricing Fields of type ‘User Defined Price’. This came to light in a donation form which I was trying to keep a simple as possible. The workaround was to add a Total Pricing Field but unfortunately that couldn’t be hid (at least though the GF settings).

I think this is a bug but I may just not understand the limitations?

https://www.ads-software.com/plugins/gravity-forms-stripe/