Applicability of income tax audit for 55 lakh turnover?

smalll firm 1 --> businessman sells goods having turnover for fy2021 just rs.55 lakhs, no cash transactions, other income (like interest income 10 lakhs), net profit margin 4% only on turnver (excluding other income). 

my view --> tax audit is applicable because less than 6% profit margin.

experts view if any? ..

big firm 1 --> however, same facts, but turnover 6 crores, then no tax audit.  so big entities can show less margin yet no tax audit for them. looks strange..?