As David says, Mac applications in Delphi are only supported using the new FireMonkey framework, as opposed to the VCL controls in previous versions of Delphi. You can still use VCL in XE2 (and later), but only for developing Windows applications. FireMonkey can be used for developing both Mac and Windows applications.
FireMonkey has a memo control, just as the VCL does, and this also has a Text property, so this line of code would be perfectly valid in both a VCL and a FireMonkey (FMX) application:
Memo1.Text := 'Line 1'#10'Line 2'#10'Line 3'#13#10'Final Line';
Where Memo1 is a VCL or FMX Memo control.
However, the VCL control (as of XE4 at least) still does not properly support the #10 (LF) line breaks, but the FMX control does, on both Windows and Mac so although the code above can be used in both VCL and FMX applications, the results will be different.
In VCL (Windows) you will get the following content in the memo:
Line 1Line 2Line 3
Line
Where as with FireMonkey on Windows and/or Mac you will get:
Line 1
Line 2
Line 3
Final Line
So the answer is that FMX behaves differently than the VCL and respects both #10 and #13#10 line break sequences, irrespective of platform where-as the VCL memo behaviour remains unchanged and is only supported on Windows.