I was a Mock trial nerd in HS, which gives me some basic legal knowledge of how the whole process works.
I'm familiar with EMU legality stuff because of SenpaiSomething the lead Dev for Project Diablo 2. Talks about this stuff on stream whenever someone complains that they need a Legally obtained CD key to play PD2. It's also what Nintendo's head Copyright Lawyer says about legal vs illegal EMUs.
I was unaware that Equitable Estoppel was a thing, but i'm familiar with what promissory Estoppel is because i own like 250k in Wizard Poker cards. It's the same basic principle, you can't say one thing in public then say the opposite in court. Daybreak can't say we think EMUs are great and they make our IP more valuable in interviews. Then say they violate our copyright in court and cause harm. They can't say you're allowed to Changed the serverhost.txt file on their public forums. Then say you can't change it in court. This ruins every part of their case besides trademark infringment. Daybreaks case will get tossed because of lack of evidence.