Setting Router/Switch Code On Primary and Secondary

[system_admin_jk]

I have a VAR who setup an ICX-7450 and I'm interested in what the best practice is.

He put router code on the primary and switch code on the secondary.  He set it to always boot from secondary as that is where the config is.

Is this as odd as it seems to me and can someone point me to best practices regarding primary/secondary partitions.

Thanks.