The lust check for masturbation seems to be on entering the menu and not the actual masturbation type.
If you are lactating, you can access the masturbation menu (ok) and hand milk (ok), but you can also select "Vaginal" (this Steele happens to have a vagina) and the scene will play at 0 lust. Dildos still check when accessed from the Inventory (and do not show up in the Masturbation menu). I did not test masturbating with a dildo and then hitting "Repeat"
Reproduction:
Load save, masturbate, then select masturbation again. See that Vaginal works.
If you are lactating, you can access the masturbation menu (ok) and hand milk (ok), but you can also select "Vaginal" (this Steele happens to have a vagina) and the scene will play at 0 lust. Dildos still check when accessed from the Inventory (and do not show up in the Masturbation menu). I did not test masturbating with a dildo and then hitting "Repeat"
Reproduction:
Load save, masturbate, then select masturbation again. See that Vaginal works.