Wait wait wait...original poster plz post the memo on here ...this isn't making much sense. I think you read it wrong...the company made an error...or you are taking second hand information as fact...
De-Ice is different than Anti-Ice
I have flown operations that allow up to enough ice that you can clearly identify rivets and letters through the ice...( I always requested full body DEICE type 1) whatever that is...
Now with the unpressurized take off...I don't know because I haven't read this document...
The only thing I can think of is that it's just another way of keeping DEICE fluid out of the packs...but there are better ways of skinning a cat right?
Plz post the letter from company for us.