No; it is a tangible benefit. It's far more than seconds.
When it was first used for CAT III, every MLS aircraft saved 1nm. With up to 25% of arrivals MLS equipped, landing rate in LVP could go from 24 per hour to 26-28. Not to be sniffed at in terms of delay profile.
GLS does not offer this benefit at all currently; I would be surprised if the first public transport CAT III GAST-D approach was made before 2021. At current pace, maybe '22 or '23?
And of those GLS-equipped aircraft flying today, how many are GAST-D? Not many, if any at all. So they will all need a software, if not a hardware upgrade before they can fly CAT III approaches.
In the meantime, wide aparture array ILS is the way forwards.