I thought about the same, but these are at their own discretion they can deny or accept the loan or change their terms of HELOC.
First, appraisal is always working against a borrower as most the refinancing appraisal comes 10% less than actual price. Lender have built-in advantage on low appraisal value.
They can estimate appreciation and bet on safer appreciation potential homes than others.
Similarly, they can choose borrower who is wealthy and better for long term than going with anyone less than 700 FICO.
They still have the risk of 2nd lien when economy goes south.
However, my question is who wants to give appreciation to them, esp well placed investor or primary owners?