Unless a score is articulated, defaults need to exist.
In my view, defaults, plural, need to and do exist, one for each style and tempo of piece - not one universal default. Legato first beats for waltzes and short first beats for polkas is a convenient example.
I've checked three different method books (Palmer-Hughes, Magnate method, Pietro Deiro method book). They all mention chords to be played short and not at full quarter note value.
I checked the four I had handy and reached a different conclusion. (I omitted this from my last post with the hope it would defuse things a bit and keep it shorter...)
Palmer-Hughes 1 says "play these notes short!" in the example where it introduces the waltz rhythm - without saying if it means only that exercise, or all waltz rhythms, or all pieces period. (I think it's obvious it means either the first or second, but it doesn't say.) It then doesn't mention it again. I think this is a bit of a defect. It SHOULD mention it again at the first 4/4 piece 20 pages later, or in the book 1 quiz, or in the book 2 left hand review.
Galliano introduces the basses with sustained-chord exercises, then 'slow, even and separated' oom-pah lines, and then doesn't say what he intends on the early both-hands exercises. But his recording plays both single notes and chords very short, so presumably he intends that. (Later in the book there are pieces where he contrasts eighths-and-rests with quarter-note basses.)
Anzaghi introduces staccato after 10 pages of legato bass-chord exercises, and says it is indicated by a dot. He continues to specify 'fairly legato sound' for many following exercises. When he wants staccato he writes dots or he writes eighth-note chords followed by rests, throughout the whole book. Staccato drills, for both hands, appear more than 100 pages in. The "bass note held through the bar, chords very short" variation you use at the end of your video appears on page 125 (and is notated with a dotted-half downbeat and eighth note-eighth rest chords.)
Würthner (yes -- he's old, but he's still often used by German speakers, especially if they play B system) introduces single sustained chords, then sustained chords accompanying hymns, then introduces articulation in the following chapter. After defining legato, portato, and staccato, he comments that portato is a default for unmarked single-note passages, and sets legato single notes and portato chords as his default for oom-pah-pah patterns.
This leaves me with the feeling that the obsession with everything staccato is either very recent or very USA-centric or both. I'd like to think it's confined to people who only play waltzes and polkas, or confined to people on instruments with no register switches and too many bass reeds.
Of course you won't be surprised to hear that the first book I studied from was Anzaghi's.