It will be interesting to see how effective it is, I got around Netflix by just using browser versions. They did a shit job and haven't bothered to fix it.
Can you imagine if a streaming service did something good? "We're updating the terms of service. Now each profile under your account can have their own usernames and passwords to access the service, the profile limit has been doubled, and the number of concurrent logins per profile tripled!"
Honestly keeping it kinda fuzzy and not cracking down is the best option for them.
Some people just aren't willing to pay full price for Disney+. But if they can share their account with someone else, they can pay half price. Most of the cost is in producing the content so having two people paying half price instead of zero people paying full price is a win for them.
But not explicitly allowing this means there's a lot of people that won't share their account. I got sticklers in my family like that... meanwhile my Netflix password is on a note on my parent's fridge. Anyway the sticklers pay full price, the people that don't want to pay full price are still paying something, this maximizes the revenue.
But they're being stupid and think cracking down will convert two people sharing an account into two accounts paying the full price. But it's more likely to convert two people sharing one paid account into zero paid accounts.