What's the purpose of egg white in this sherbet recipe?

I've been making a buttermilk sherbet for decades from a recipe an old friend gave me:

Mix:
2 cups buttermilk
1/2 cup sugar
8 oz crushed pineapple with juice
1 tsp vanilla
Dash salt
Freeze in tray till mushy.
Beat 1 egg white till stiff, add 1/4 cup sugar, and fold into stirred pineapple mixture. Return to freezer. Set out about 10 minutes before serving.

We make it in our ice cream maker, instead of the freezer tray method. When I make it, I beat the egg white till it's stiff, as the recipe says, add the sugar and stir it in. When Mr. Kitchen makes it, he whips the whites till they're kind of foamy, adds the sugar and stirs that in. It goes in the bowl as soon as the other ingredients are mixed together, then into the machine.

So does the egg white serve any function since we're not doing the still-freezing method? I feel like it must add body, so the stiff whipping helps. Mr. says the machine stirs air into it anyway, so it doesn't need whipping so much.
I guess this is a physics question, more than a flavor question, really. But I also think that it would give a bit of meringue flavor to it, and I love meringue.