Returning a Boolean will not indicate the exact cause.
Correct behaviour is to raise an exception, being the exception class and properties the info about the problem.

See for example Classes.pas TStrings LoadFromFile:

procedure TStrings.LoadFromFile(const FileName: string);
var
  Stream: TStream;
begin
  Stream := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
  try
    LoadFromStream(Stream);
  finally
    Stream.Free;
  end;
end;


OurTTeeSeriesSourceFile.LoadFromFile, TImportChart.LoadFromFile and TeeStore.pas unit LoadChartFromFile, all use the RTL default TFileStream classes.

A custom function can always "eat" the exception and return a boolean, if desired:

uses
  TeeStore;

function Load(const AChart:TCustomChart; const AFile:String):Boolean;
begin
  try
    LoadChartFromFile(AChart,AFile);
    result:=True;
  except
    on Exception do
    begin
      // EAT
      result:=False;
    end;
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  if Load(Chart1,'test.tee') then
     Caption:='OK'
  else
     Caption:='BAD';
end;

However, this is not recommended. Exceptions must surface-up to callers.