A preferred return means limited partners get paid first, up to a stated rate, before the sponsor takes any share of the profit. In your deal, cash available for distribution goes to the LPs until they've received the equivalent of 8 percent a year on the money they contributed. Cash beyond that splits 70 to the LPs and 30 to the sponsor.
The coupon comparison is where your friend is off. A bond coupon is a debt payment and missing it is a default. A pref is a position in the payment line. If the property doesn't generate cash, there is nothing to distribute and nobody has breached anything, which is exactly why the deck can project zero in year one and still call it a pref.
Two words decide what a missed year costs you. Cumulative means the unpaid pref accrues and has to be caught up later, usually out of refinance or sale proceeds. Non-cumulative means the missed year is gone for good. Then check whether it's simple or compounding, because over a five year hold that wording moves real money.
The part that surprises people later: the pref is normally calculated on unreturned capital. If the sponsor returns half your capital at a refinance, the pref from then on is calculated on the smaller balance, so your quarterly distribution drops even though the deal is going well. Read the distribution waterfall and the definition of unreturned capital side by side. Separately they both look harmless.