You actually have it kind of backwards I think. The TV will do what it does regardless of the signal (so long as it's an NTSC signal). The signal is produced to the standard so that the TV can handle it.
The NTSC GC/Wii uses 525 lines. That is the NTSC standard, that is what all NTSC devices use. NTSC spec display devices have an active display area of 486 lines. They will display 486 of the 525 lines in an NTSC signal. The GC/Wii renders @480 lines (sometimes less). This means that there are some active lines that contain no image data, but are part of the active frame. A proper NTSC TV will display 486 lines, of which 480 (or less) will actually contain video data. Whether or not there is actual video data there is irrelevant in terms of determining the SAR of the display. So 486 is the number of horizontal lines in the 4:3 display.
Devices can handle 720 samples, but the standard is that the active line duration is 52.6555 µs, which, when multiplied by the sample rate of 13.5 MHz, gives you an active display width of 710.85 samples. The 13.5MHz number can be obtained by multiplying 30*1000/1001 (the NTSC frame rate) by 525 (the number of lines per frame) by 858 (the width of a complete line in samples). This means that a perfect 4:3 NTSC spec TV will display 710.85 samples per line. If a 4:3 TV is perfectly matched to the NTSC spec, it will display 710.85 samples on 486 lines and cover a 4:3 total area. It doesn't matter if the GC/Wii actually renders only 640x480 or 448 or whatever number of lines, 486 lines will be displayed with 710.85 samples per line according to the specification. This means that each sample has a SAR of 4320/4739. Sorry if my explanation is convoluted and hard to follow, there's just so much going on that has to be accounted for. If something doesn't make sense, please point it out so that it can be clarified/corrected, but I am fairly sure that my thought process is sound.
The NTSC GC/Wii uses 525 lines. That is the NTSC standard, that is what all NTSC devices use. NTSC spec display devices have an active display area of 486 lines. They will display 486 of the 525 lines in an NTSC signal. The GC/Wii renders @480 lines (sometimes less). This means that there are some active lines that contain no image data, but are part of the active frame. A proper NTSC TV will display 486 lines, of which 480 (or less) will actually contain video data. Whether or not there is actual video data there is irrelevant in terms of determining the SAR of the display. So 486 is the number of horizontal lines in the 4:3 display.
Devices can handle 720 samples, but the standard is that the active line duration is 52.6555 µs, which, when multiplied by the sample rate of 13.5 MHz, gives you an active display width of 710.85 samples. The 13.5MHz number can be obtained by multiplying 30*1000/1001 (the NTSC frame rate) by 525 (the number of lines per frame) by 858 (the width of a complete line in samples). This means that a perfect 4:3 NTSC spec TV will display 710.85 samples per line. If a 4:3 TV is perfectly matched to the NTSC spec, it will display 710.85 samples on 486 lines and cover a 4:3 total area. It doesn't matter if the GC/Wii actually renders only 640x480 or 448 or whatever number of lines, 486 lines will be displayed with 710.85 samples per line according to the specification. This means that each sample has a SAR of 4320/4739. Sorry if my explanation is convoluted and hard to follow, there's just so much going on that has to be accounted for. If something doesn't make sense, please point it out so that it can be clarified/corrected, but I am fairly sure that my thought process is sound.