Could the hole be used to anchor the guitar during spraying?
Great question, actually! I've seen a pic of a guitar being sprayed in Westerly but can't recall how it was supported.
Still, while I see the economic benefit of using a universal neck block, I also think that models using true dovetail joints would benefit from having a completely solid and thus stronger block, besides the acoustic properties.
But that could be another explanation for that "hole".
I also wondered if perhaps it was to enable easier disassembly for a neck reset, maybe a better steam/heat injection point? (Although we know they went to Titebond for necksets in NH, I don't recall hearing what they might be using in Oxnard)
It'd be instructive to compare it to a D55's block because as of yesterday and this morning, Guild's website does NOT show the F55 as using a dovetail that they specifically mention for the D55 and the Traditional D40:
http://guildguitars.com/g/f-55-in-natural/
This might be an oversight or spec'd elsewhere but one wonders why it's not shown in the description when they took pains to include it in the other 2 descriptions:
D55:
"The D-55 remains true to all the premium appointments of its 1968 predecessor, including a AAA Sitka spruce top, solid Indian Rosewood back and sides, ebony fingerboard and bridge, and nitrocellulose finish. Internal refinements include scalloped Adirondack bracing as well as
an improved dovetail neck-joint, hand fit to make this generation of D-55 the lightest, loudest, and best-sounding yet."
D40 Trad.:
"The D-40 Traditional’s three piece mahogany and walnut neck is topped with an Indian rosewood fingerboard and is
joined to the body with an authentic dovetail joint"