@Troy, I can't rule out if it's the same activity or not without knowledge of either. However, I don't believe there's a world of difference between the two. If someone engages in sexual activity whether it's solo, a commercial pursuit, domestic or casual - there's still a level of intimacy. People say "It's just sex" and while that phrase may be true, I've learned that we humans can turn the most perfunctory behavior into a habit.
Also "servicing" comes in many forms to satisfy psychological needs. If we're in an intimate relationship I don't believe our spouses shouldn't be kept in the dark.
Case in point, I enjoy cooking for my family and sitting down to eat a great meal with them. I also snack on junk food that has no nutritional value, eat chips in bed when I'm really not hungry. I enjoy going to great restaurants and can easily spend almost $100 on a meal. All are pleasurable to me...but if I'm 100 lbs overweight, obviously being serviced by food is a sign there's psychological distress.
With food intake, or lack thereof, there are physical signs so it's difficult to hide this activity from my spouse. If I hide my sex servicing activity (unless it leads to STD or a baby,) from my spouse, then we're not intimate. He's just a roommate and not a very close one at that.
By the way, I've never really known any man to hide his masturbation habits from me,. Not really sure what I should read into that lol