definitely assumed that everybody interpreted 'sex routine' as a scheduled frequency per week a partner (typically female) agrees to have sex with their partner (typically male), in order to fulfill her duty so she's not responsible when he cheats
That is so much worse than my original misinterpretation, where I was thinking along the lines of a gym routine (as in MWF) instead of a gym routine (squats/pushups/hip-flexors).
Until I read the comments, I assumed a "sex routine" was like having a certain habitual progression of activities during sex, or habitual ways to initiate sex with your partner.
But... so many ways to interpret this.