SYR has several warnings and precautions about how and when to properly ship an animal, posted all over the website. A person who does so improperly using SYR will also do so if they are certified. Just because a person gets certified in the summer doesn't mean they will use the proper procedures in the middle of winter.
An idiot will be an idiot regardless of which course or path they use to be an idiot. The buyer needs to make the extra effort to ensure they are getting an animal from a reputable and knowledgeable seller that they can trust. Whether the seller is certified or uses SYR makes no difference and provides no reassurances. At least with SYR there is a guarantee. If something goes wrong with a certified shipper who uses improper procedures, you are stuck negotiating with that same person.