Why is `if x is None: pass` faster than `x is None` alone?

Timing results in Python 3.12 (and similar with 3.11 and 3.13 on different machines):

When x = None:13.8 ns  x is None10.1 ns  if x is None: passWhen x = True:13.9 ns  x is None11.1 ns  if x is None: pass

How can doing more take less time?

Why is if x is None: pass faster, when it does the same x is None check and then additionally checks the truth value of the result (and does or skips the pass)?

Times on other versions/machines:

• Python 3.11: (12.4, 9.3) and (12.0, 8.8)
• Python 3.13: (12.7, 9.9) and (12.7, 9.6)

Benchmark script (Attempt This Online!):

from timeit import repeatimport sysfor x in None, True:    print(f'When {x = }:')    for code in ['x is None', 'if x is None: pass'] * 2:        t = min(repeat(code, f'{x=}', repeat=100))        print(f'{t*1e3:4.1f} ns ', code)    print()print('Python:', sys.version)