Why is Adam solver an option?

[meder411]

In the paper, you report a negative result that

WGAN training becomes unstable at times when one uses a momentum based optimizer such as Adam [8] (with B1 > 0) on the critic, or when one uses high learning rates

You advocate using RMSProp for the discriminator instead. Yet in the implementation, although RMSProp is the default, there is an option to use Adam (line 144). Is this included for consistency with your evaluation, or have you found settings for which Adam is effective with the WGAN?