(How) Can I read P1 data with REST calls?

As an iOS user I would like to read P1 sensor data (current energy/gas consumption ) stored on my Homey (via the P1 Smartmeter App) using REST calls from Shortcuts or Scriptable.

While there is a “Web API”, it looks like the P1 App should support this. Unfortunately it only supports POST requests; no GET requests.

Would I have to ask the author to support this? (Or fork it myself?)

Or is there another way to achieve what I want? (Can you get energy data directly from Homey?)