Late for what exactly?
Common now ... there's at least 5 to 6 aero positions needing to be filled according to the website. From the looks of the descriptions these aren't even management positions ... these are the grunt work people who you need to get the job done. The W04 is being unveiled in a few weeks. Unless most or all those Aero positions are for the W05 ( and I highly doubt it) The fact that SO MANY aero positions are presently open is concerning .. and yes filling them now is a tad late. (Yes I am aware of better late than never).
These are not unreasonable concerns.. Mercedes is not known for good aero development and the recruitment drive to fix this really does appear to be late. Especially if well qualified personnel are hard to find.
Hence the comments made above.