Part of the reason is included in the statement: "Advise them that these types of PPE are safety concerns, especially tents / pods which can slow access to crit

Part of the reason is included in the statement: "Advise them that these types of PPE are safety concerns, especially tents / pods which can slow access to critical safety procedures, including emergency evacuations and use of oxygen masks" Note that in-flight crew are generally tasked with getting everyone evacuated, so making their job more difficult endangers more than just the pod-wearer.