clarification of warning about data and catalog paths

Page 23 of installation guide says:

"Do not use a single directory to contain both catalog and data files."
https://my.vertica.com/docs/7.1.x/PDF/HP_Vertica_7.1.x_Install_Guide.pdf

This suggests that the -c and -D options of "bin/adminTools create_db" when creating vertica DB should specify different values.

According to https://my.vertica.com/docs/7.1.x/PDF/HP_Vertica_7.1.x_GettingStarted.pdf at the bottom of page 20 and the top of page 21,
the default directory for catalog is /home/dbadmin and the default for data is /home/dbadmin.

Question:
1. Is having the default layout described in the GettingStarted guide unsupported, or undesireable?

2. Is it a bad thing to have catalog path and data path the same?  If so, what is the reason?

3. Is it advantageous or unimportant to have catalog and data mounted on their own drive each?

thanks

kesten