I guess it makes sense on the short term. Instead of application - you work for (as quoted) 6 weeks to prove yourself and you either get fired or not.

But on the long term? Senior-level employee makes an error? Bam - fired! With all the institutional knowledge gathered over the years, experience, etc. If it was a major screw-up - you'll be firing an employee who will not do that mistake again, but you will risk it with a new hire.