Wouldn’t wrist position be considered part of your overall posture?
There are far more factors determining wrist position than the size of the keyboard, and only a very small fraction of all keyboard users end up developing any form of issue.
Moreover, I'd wager that the number of people enduring bad laptop keyboards greatly outnumber those developing any kind of RSI issue, let alone those who feel strongly enough to buy ergonomic keyboards.
It would be interesting to see how many ergonomic keyboards end up being snakeoil preying on people with more disposable money than good judgement.