Umm... How would you describe, say, a 170 MHz sine signal sampled at 312 MSa/s, when shown in dot mode or with linear interpolation? It would look severely misleading in my book. Sinc interpolation is not the issue here.
and you keep showing the worst case scenario to prove your point when user really fucked up trying to probe >170MHz using 4CH cluelessly. in reality we will avoid such test condition. we will turn on only 2 or 1 channel in operation. even if we have to use all 4CH, when in doubt, we can switch to 1CH to probe the suspicious high frequency signal. granted its not foolproof, thats why you have to gain knowledge and theories as you go, otherwise if you keep doing your setup example you mentioned again and again and made mistake again and again, this job is actually not for you, ymmv.
170 MHz folds back to 142 MHz in the first Nyquist zone. So it looks like you had sampled a 142 MHz sine wave.
if you really try to probe 170MHz fundamentals at 312 MSa/s really you have something wrong within you, not the scope, scope is just a tool. usually spectral content in excess of Nyquist limit are harmonics whose magnitudes are much smaller hence aliasing will not affect much the fundamentals shape, unless your circuit is oscillating unexpectedly. ymmv.
analogy is manual transmission car vs automatic transmission car. manual is not foolproof, automatic transmission is, but for some people like us, we still prefer manual and know what we are doing, and also know what we should not do. because we need performance not available in automatic cars. ymmv.
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