I think liquidity could be the main issue here, but is it a typo or something where you mentioned the support team is available 20 hours day? I mean if I'm not wrong it should be available 24 hours a day by default not 20 hours a day.
It usually means that they have a limited team that can solve problems and therefore may not be available 24 hours a day.
It is good as it means that they get a response in less than 4 hours, which is very good.
They can use AI to get instant responses, but I prefer dealing with a human employee to solve problems.
4 hours a day means one more person in the support team. That means additional costs. I am sure that there are periods during the day when there is less activity on the exchange, so it can be a period without direct monitoring by support.
I agree that it is better to have 24/7 support, but at least we got an honest answer here, even if it was about minimising expenses. And in the end, this also shows care for the service itself.
