UPVC French Door Frame Material Inconsistency

[bobajob2018]

Hi. Can anyone advise as to what is going on in this picture?! I am having a garage conversion done and the white UPVC French Doors have a metal (aluminium?) bottom rail/frame which doesn’t match the rest of the installation. Before I get fobbed off by the manufacturer and/or builder, I am trying to work out whether:
1) the manufacturer has run out of UPVC and substituted with a metal frame in instead?
2) the metal frame is normal (perhaps more durable) and should have a thin upvc glue-on covering that has been missed.

Any advice so that I can take the right line with the builder/manufacturer would be greatly appreciated.

 

[crank39]

That's a low profile aluminum threshold, some manufacturers ask the question whether a low threshold is required if not then the same section is used as the top and sides, others may fit them as standard, it's either or really so nothing untoward has happened, depends what was specd

 

[bobajob2018]

Thanks @crank39 that puts my mind at rest! - Do you know if these can be painted to match (and if so, what type of paint) or do people typically leave the metal finish as is? It’s not very noticeable from the outside because of the door overlap conceals most of it, but I suspect it will be noticeable from the inside. The builder did give me the option of normal vs low-profile, just didn’t mention anything about it being a different material!

 

[crank39]

It's anodized aluminum so will probably not accept paint very well, would also wear away over time