It is all true then.
The original Wby DGR .375 Wby without the drop floorplate was 3+1.
They used the drop floorplate on the .378 Wby, .416 Wby and .460 Wby for also 3+1.
Lately they have replaced the Wisner rear sight with one by NECG,
and they are using a drop floorplate on the H&H-based chamberings,
but limiting the capacity to 3+1 with the follower and springs used.
That is silly, that's my point.
I have a circa 1985-1986 Fibermark Wby Mark V .340 Wby.
That was the first factory rifle for big game with a synthetic stock.
McMillan did it with black wrinkle paint back then, before they learned to do the McSwirly finish.
I have tried that drop floorplate, ordered from Weatherby Custom Shop on the .340 Wby.
Yes indeed, easy 4+1,
just like on your .375 Wby DGR.
Just need the original follower and spring and add the drop floorplate, which is a pocket plate or coffin plate.
That drop floor plate also converted my .30/.378 Mark V Synthetic from 2+1 to 3+1 when I re-barreled it to .510/.338 Lapua Improved.
I understand.
That "then new" old .340 Wby Fibermark accompanied me on my first trip to Kodiak in August 1986,
then on a solo caribou hunt for a week on the Alaska Peninsula in November 1986.
Second trip to Kodiak in 1987, I had a .375 WBY.
I should've had a Four Five Eight,
luckily I lived to tell of it anyway.