Very much no. A lot of them are, somewhat sadly but predictably, targeted at larger markets and therefore pull data from NOAA for the US, the UK Met, and the Ge

Very much no. A lot of them are, somewhat sadly but predictably, targeted at larger markets and therefore pull data from NOAA for the US, the UK Met, and the German weather service (DWD), etc. but then fill in the gaps with something like NOAA that will provide predictions for everywhere in the world. You also quickly get into different models that are used by different services, usually because they work better in the specific environment they're targeting. For instance, Estonia and Finland, possibly with some others, collaborate on their own weather model that works pretty well in the Baltics. There are also highly-regarded models like the ones provided by ECMWF that are only available for a fee, so a lot of apps won't include them, instead preferring to simply use NOAA because it's free for everywhere.