Does late arrival give you more of a chance of an upgrade?

I arrived at the Sofitel Melbourne, Australia a week or two ago around 8pm. I had booked a fairly standard room for a single Tuesday night. On checking in, I got an upgrade to a suite. I could have had 5 of my best Melbourne friends round for dinner, given that the suite had a dining room table seating 6, and a lounge with enough room for the same.

You can see the size compared to standard rooms on the fire exit map (or room envy map as I think of it).

I think I have only stayed at one other Sofitel this year (in Brisbane, for a night), but I do have a Silver  Le Club card.

So, is it the status (lucky to be near the top of the tree that evening), or the late arrival (stuck all the other pax in standard rooms, and only had better rooms left) that got me the upgrade?

Also – why is it that you always get upgrades, when your travelling alone, and for a stay of less than 12 hours, or is that just a kind of Murphy’s law?

I might just start flying out on later flights and see . . .