Why are Shapiro-Wilk and Kolmogorov-Smirnov test compared with same sample size? I am trying to understand when to use Shapiro-Wilk Test and/or Kolmogorov-Smirnov Test for normality. Currently, I am following this website How to Test for Normality in R (4 Methods). This paper Descriptive Statistics and Normality Tests for Statistical Data says:

The Shapiro–Wilk test is more appropriate method for small sample
sizes (<50 samples) although it can also be handling on larger sample
size while Kolmogorov–Smirnov test is used for n ≥50. For both of the
above tests, null hypothesis states that data are taken from normal
distributed population.

So it suggests using the Kolmogorov-Smirnov test for a sample size bigger than 50 is more appropriate. While the website I mentioned above, uses the same sample size for both tests to check normality. I don't understand why
Also from this What is the difference between the Shapiro–Wilk test of normality and the Kolmogorov–Smirnov test of normality? and answer, it seems that you can't actually compare the tests.
So I was wondering why the website is comparing the same sample size for normality and when is it not possible to use Shapiro-Wilk test anymore?

I presume that by the Kolmogorov-Smirnov they actually mean the Lilliefors test -- the estimated-parameter version for the normal case that was tabulated by Lilliefors; he did tables for the exponential as well. This (calling Lilliefors' modification for estimated parameters "Kolmogorov-Smirnov") seems to come mostly from SPSS; many authors follow its lead. This has been the cause of many confusions.
The Lilliefors can be compared to the Shapiro Wilk, since they're both tests of normality with unspecified parameters.
Which one is preferable depends on which alternatives you seek power against (and, occasionally, sample size can make some difference).
Often in the sorts of situations people tend to consider in power comparisons - but not always - the Shapiro-Wilk will come out with higher power. In some such cases the Lilliefors has better power, though.

The Shapiro–Wilk test is more appropriate method for small sample sizes (<50 samples) although it can also be handling on larger sample size while Kolmogorov–Smirnov test is used for n ≥50. For both of the above tests, null hypothesis states that data are taken from normal distributed population.

This is poor advice; you can find it in many places, but it stems from the simple fact that Shapiro and Wilk themselves only produced tables to $n=50$, over half a century ago, as if nobody had done any work on it since.
Naturally, that is not the case. Computer functions that will work for much, much larger $n$ have been available for decades. The version of the test that is implemented in R goes out to $n=5000$, using Patrick Royston's algorithms from papers published in 1982 and 1995. The usual advice when you go beyond the end of available Shapiro-Wilk functionality is to use a Shapiro-Francia test.
There's nothing that happens at $n=50$ for a wide variety of alternatives that would change the considerations of which test you might use. If you were in some situation where the Shapiro-Wilk is the better test at $n=45$, it's (nearly always) going to be the better option at $n=55$ and $n=75$ as well.
It's important to be aware that there are dozens of tests that could be used besides these two, and if broad power against likely alternatives of interest is what you care about, I would tend to avoid both these tests as there are other tests that do typically better in most of the situations these do well at (among the situations that people tend to worry about). If you like the Shapiro-Wilk, why not Chen-Shapiro? If you like ECDF-related tests, why not the version of the Anderson-Darling adjusted for parameter estimation? There are many other possibilities besides.
I will add my support for Nick Cox's comments above. Graphical methods come closer to addressing relevant considerations if you're worried about whether the normality assumption for some test should be of concern (at least if you're in a situation where avoiding letting the data choose the hypothesis is impossible to avoid, which would be fairly rare).
