Migrate to Business Central On-Premises

I asked a to A partner to migrate my NAV 2015 to Business Central On primeses. We have a lot of customizations iN C/AL code. They say me that they must upgrade this way: 

2015 to 2016

2016 to 2017

2017 to 2018

2018 to BC On Premises

But in this URL I understand I can go to BC OnPremises directly from NAV 2015

https://docs.microsoft.com/en-us/dynamics365/business-central/dev-itpro/upgrade/upgrading-to-business-central-on-premises

What do you think about?

Thanks