MOV's (metal oxide varistor) protect against 'transient spikes'
that is a very split second high voltage spike,
consider it like an airbag in your car against sudden impact of an accident
a surge while not usually as high a voltage as a spike
is more like a title wave and it can last minutes even hours, and will burn out motors , transformers, any thing with a voltage operated coil
although low voltage brownouts happen more often sustained higher than normal voltage surges
you want to suppress a surge (lower the voltage) or disconnect aka go offline
you want to Boost low voltage if possible
i think saying the hughs has surge protection is a stretch of marketing speak
the expendable replaceable MOV's are Transient spike protection