count(*) should be different from count(column)

[JsToCode]

I use cosette online to prove the count projection equivalence. The answer should be not equivalent. Because count(*) will include NULL value, while count(column) will exclude NULL value.
The following is the code:

schema s(a:int, b:int);
table r(s);
query q1 -- define query q1
select count(*) as a from r x;

query q2 -- define query q2 likewise
select count(y.b) from r y;

verify q1 q2;

There should be not equivalent if there exist some NULL values in y.b column. Even the int type, we can still set default value to NULL, not 0.