It is unusaul for a bank the size of HBAN to portfolio mortgages if they qualify for a program where they sell the loan and retain servicing rights. Historically, a 15 year or 30 year mortgage would have an average life of 5 to 8 years. Loans that are made at these levels will not likely ever be refinanced, so they will likely be on the books much longer than in prior years. This would make a huge risk to the bank when interest rates on deposits rise - even if it does not happen for several years. HBAN would be better off to shrink deposits in the bank rather than retain 15 to 30 year loans under 5%. I know some divisions of Park National are offering 15 year mortgages that they will retain rather than sell - seems like an act of quiet desperation indicating they must have virtually no pipeline of meaningful commercial loans. Hard to see how that can work out for them.
Not all loans are fixed rate. Adjustable rates are very common especially if a loan starts with low rate. Convertible loans are also popular where they convert to fix after 5 years or other terms. Banks do their research and calculation before they get into any program. Even JPM sell their loans. It did it to me so HBAN can do the same.