Ariston Point of Use Water Heater Requirements

I am building a house and want to install an Ariston point of use inline water heater to serve the master bath since the room is far from the whole house water heater.
My plumber is telling me that I will need to have both pop off and drain lines installed for this Ariston heater and that it will need to have a drain pan. I understand the need for a drain pan, but I was under the impression that these sort of small water heaters were self contained and easy to drop in after the fact (without the need for separate drain and pop off lines).
The plumber also mentioned the local code may call for this (Austin, TX)
What is the dirt on these mini water heaters and is my plumber wrong or right?
Thanks, Brightstar65
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