I personally would add it on both sides of the equation, to your income and your savings I don't because I have a $100 match per year.
I thought it says to look at your savings as a % of your take home pay, and take home pay is gross pay minus taxes. I'm not grossing that 5% match.
If you're going to count the 5% match as savings, you either also add it to income, or the table / time to retirement computation will be overly optimistic.
If you're at say 50% without this match, then when you add it in, you have 2 options:
Count only in savings. Savings rate is now 55% / 100% = 55%
Count in savings and income. Savings rate is now 55% / 105% = 52%
Now, since we're only talking about 5%, that is not a huge difference, but what if your employer ups the ante and you're suddenly getting a 10% match.
60/100 = 60%
60/110 = 54%
Looking at the table in the article, that is a full 2 years different in the projected time to retirement.