Not quite true - ISOs can incur AMT at time of exercise, which is kind of complicated and doesn't always create a tax burden. In the $100k range, it probably will, but they'd have to do the calculation to find out.

https://www.esofund.com/blog/amt-tax

Regardless, they'll still have to front the $ to exercise and be left with illiquid stock. It's not a good situation.

He’s being hit by the AMT due to the value of the options. If you’re hit by the AMT, you’ll owe taxes on the spread between the strike and FMV on exercise, even though you haven’t sold them.

As others have said, AMT doesn't respect ISOs, which makes ISOs pretty useless.

Not entirely, if you don't owe AMT in subsequent tax years then you get the money back as a tax credit.

https://www.kiplinger.com/article/taxes/t055-c000-s001-the-a...

Hmm, I'm not sure - how would I tell if they're classified as ISOs?

It would be in your grant letter explaining the number of options and the strike price.