That system will not distribute air properly and the homeowner is probably does not enjoy the comfort that they “paid” for.
The static pressure drop through flex duct is more than a hard piped system and the resistance really increases if flex duct is not pulled tight, pinched or loops around other things. It is necessary at times but not preferred for all duct branches.
A competent HVAC contractor will install duct per SMACNA standards.
I would simply recommend they have that looked at by a competent HVAC contractor.
it may work but almost looks like unacceptable workman ship .may take up way too much room in basement.Is that corroded vent connector pipe at bottom of picture? I did hvac install for 20 yrs. balance dampers installed cant see that? room for a/c coil? Is insulated flex strapped every 4ft or close to that so not hanging down?
Very few basements in Ok the unit was in a high pitched attic upflow standing straight up. Home was less than a year old in a high end district. Most of this younger generation can not pour P I S S from a boot with the directions on the heel;-)