I've gotten a Linux-certified Dell laptop via an old employer (I bought the device when I left the company), and even after over four years, Dell is still pushing firmware updates.
Time wil tell if Lenovo will do the same. It could be the source of the additional "cost", or just Dell using the OS for its margins.
Yes,
apt-get update
is, to the best of my knowledge, functionally identical toapt update
.