Actually that pronunciation of the dark L is common in some parts of London and the East Midlands of England (which are the two places I spent my childhood).
So I pronounce many such L sounds as a sort of w sound, depending on how lazily I am speaking, and to whom.
It’s very common to hear the Ls in words like milk, soul, solder, bill, &c replaced with a clipped w sound, but usually only when followed by a consonant sound.
So, a killer is some who kihws, the bihw-payer uses dollars, the foohw commits folly, etc.
And certainly in the West Country, at least in Bristol and Gloucester, they do a similar thing, but with a more drawn out ohw- sound, and the American accent certainly has other resemblances to the West Country accent.
It’s difficult to explain, but I think you know what I mean.
So, the L-vocalisation is part of several dialects in England, which pretty much totally legitimises such pronunciation in American.
the “correct” way to pronounce these words (including solder) is with the L, but it’s common in America and some parts of England to pronounce it as a kind of vowel-W.
Pall Mall -> Paow Maow
Trolley stays the same, but troll becomes trohw.
Another common thing is to replace mid/end word ‘T’s with a glottal stop,
So “battle” becomes “ba’ohw”.