This doesn't really have anything to do with rules. That's a bit of a red herring. The real issue, I tend to think, is just that to some folks (including me), that bass note at 0:12 sounds weak. Not because it breaks some rule, but just because it doesn't sound that good.
To me that note at 0:12 seems pretty obviously a clam, not a grace note or a passing tone. The nicest way of putting it is that it's a less-than-convincing musical choice. I don't quite get the scramble to figure out some way of justifying it. It's just not that good a note in that moment. That's not the end of the world.
But also I don't much care. It's such a relatively small thing that it doesn't drag down the track at all, and the bass is strong throughout all the rest of the song. No point in making a mountain out of a molehill ... but also no point in acting as if the molehill isn't there.
As you said, "to some folks it sounds weak." That's an opinion and you are entitled to it. I don't hear it as weak at all. I listen to the same passage and think grace note, specifically an acciaccatura:
"Acciaccatura
Acciaccatura (
Invalid Link Removed:
/əˌtʃækəˈtjʊərə/,
US:
/-tʃɑːkə-/; Italian:
[attʃakkaˈtuːra]) comes from the Italian verb
acciaccare, "to crush". In the eighteenth century, it was an ornament applied to any of the main notes of arpeggiated chords, either a tone or semitone below the chord tone, struck simultaneously with it and then immediately released. Hence the German translation
Zusammenschlag (together-stroke).
[4]
In the nineteenth century, the acciaccatura (sometimes called
short appoggiatura) came to be a shorter variant of the
long appoggiatura, where the delay of the principal note is quick. It is written using a grace note (often a quaver, or
eighth note), with an oblique stroke through the stem. The
acciaccatura in the Classical period is usually performed before the beat and the emphasis is on the main note not the grace note. The
appoggiatura long or short has the emphasis on the grace note.[
citation needed]
Play (
help·
info)
The exact interpretation of this will vary according to the tempo of the piece, but the following is possible:
Play (
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info)
Whether the note should be played before or on the beat is largely a question of taste and performance practice. Exceptionally, the acciaccatura may be notated in the bar preceding the note to which it is attached, showing that it is to be played before the beat.[
citation needed] (This guide to practice is unfortunately not available, of course, if the principal note does not fall at the beginning of the bar.)
The implication also varies with the composer and the period. For example,
Invalid Link Removed's and
Invalid Link Removed's long appoggiaturas are – to the eye – indistinguishable from
Invalid Link Removed's and
Prokofiev's before-the-beat acciaccaturas.[
citation needed]"
I don't know it's what John McVie intended, you don't know he fumbled. It's all "Monday morning quarterbacking". What I do know is that Fleetwood Mac, and John McVie, had been seriously successful artists for such a long time that the idea of cutting corners on the white Fleetwood Mac album is ridiculous. If it had been deemed "wrong" by John, the other members, or Keith Olsen (producer), it would have been corrected.
Greg