My mother has been ordering from Parks every single year since at LEAST 1960 and possibly earlier, and has never had a problem with their service or products (obviously occasionally there is a small packing error, like missing a packet in an order or sending two of something, but that will happen at times from any company and she never had any trouble getting it corrected). And I've ordered from Parks probably 10 times in the past 25 years myself, and never had a problem whatsoever.
Usually "spring shipping charges extra" means you ordered a live plant or tuber that cannot ship immediately with seeds and dry goods, but has to be shipped later in the spring when season is appropriate, and are charging separate shipping for that second shipment.