This is some of the things we come a cross virtually every day!
Plastic better than copper?
I'm not avert to "state of the art" but the traditionalist in me gets reinforced every day!
If the copper connector (15mm soldered tap connector) isn't lined up perfectly, which can't be done because it has to be disconnected in order to solder and safe guard the plastic threaded float valve, then this is what happens, plastic fails over a period of time due to stress.
This can and does cost enormous amounts of money repairing and making good and do we learn from this......nop.