The quote is the right way around: if you owe a million dollars ($1M) and can't pay, they'll foreclose your house and other assets and recover some of their money - it's entirely your problem.

If you owe a billion dollars ($1G) and can't pay it back, then the bank will work with you to try to get the investment back on its feet, as they will certainly not be able to recover any significant amount of it forcefully. It becomes their problem.

They may have thought G meant thousand. That’s not what I thought but it’s the only number that I could think of. Didn’t think it could mean a billion.

G is the SI prefix for "Giga", meaning 10^9. So, 1Gm is the SI representation of "1 giga meter = 1 billion meters", for example. It's most commonly used in computing, e.g. in 1GHz = 1 billion Hertz. You may have also seen it in power output numbers, such as saying that some power plant produces 1GWh annually (1 giga watt-hours = 1 billion watt-hours).

Of course, in computing G is also sometimes used to mean 2^30. The ISO has allocated the prefixes Ki/Mi/Gi (Kibi, Mebi, Gibi) for that use, so technically my machine has 16 GiB or RAM, which is slightly more than 16GB of RAM would be.

Sure, but when people talk about money, a G is usually a thousand (not talking about financial terms, just common usage)

aka "I just lost 3 G's on UST"

When's the last time you interacted with a human? $1G = ? Or $1000 at best.

Giga dollars? Get out more dude.