Do strict parents make sneaky kids?

Do you guys believe that strict parents will create sneaky kids? My sister has a 17 year old son and 18 year old daughter who she adopted 8 years ago. They are both seniors in high school and practically best friends with one another. Their curfews are 9 pm for the 17 year old and 9:45 pm for the 18 year old. They can only have social media if their mom and dad have the passwords to it. They have life360 on their phones. They can not go to their partners' houses. They can only hang out with friends if a parent will be with them. Her daughter isn't allowed to wear crop tops, ripped jeans, tank tops, skirts, or shorts. Recently my sis found out that her son was having sex with his girlfriend she flushed all of his condoms down the toilet and forced him to break up with his girlfriend. My nephew is always close with me and confides in me. He told me he didn't break up with her actually, they still have sex, and that his girlfriends dad bought them some more condoms. I told him I'm glad he and her parents trust each other. As for my niece, I am honestly not that close with her but we still talk. She has an older boyfriend (31) that her mom knows nothing about and she has an entire different wardrobe at his house. My nephew told me she is going to be moving in with him soon without saying bye to her parents. The kids bypass the life360 thing by leaving their phones somewhere and honestly those teens are just sneaky as hell lol. I always thought, are they sneaky because of their parents or are they sneaky because they just want to be rebellious? Do you guys think strictness causes sneakimess?