Is there a purpose behind strange "this will serve as" language for airline announcements?

I've been attempting to search for an explanation for the reason for the odd turn of phrase that crept into airport language in the USA 10+ years ago.

All of a sudden it seemed that common phrases like:

"This is the boarding call for flight 357 to La Guardia"

instead became:

"This will serve as the boarding call for flight 357...

I couldn't find reference to this turn of phrase online, save for it being included in a list of "annoying airline speak", ca 2006 and 2011.

I haven't come across this phrasing in any other contexts, wondering if there is some legal requirement? Some plausible deniability?

Additionally I wonder if they produce as stilted a phrase when announcing in Spanish, too.

It seems like noise words. "to serve as" is usually used to refer to an alternate or metaphorical use of something, e.g. from ODO:

The square now serves as the town's chief car park.

or from dictionary.com

This cup will serve as a sugar bowl.

But in your example, the boarding call is the normal, literal purpose of the announcement.

I think I most often hear this as:

This will serve as the last boarding call for flight ###.

so perhaps there's some nuance in the "last" qualifier that makes this less literal. Maybe it has something to do with passengers arriving at the gate at the last minute and still being allowed on.