When a version history is already loaded, decreasing the total parameter does not care. It already returns the old amount of values.

import pwb
import pywikibot as py
s = py.Site()
p = py.Page(s, 'user:xqt/Test')
x = p.getVersionHistory(total=5)
len(x)

5

x = p.getVersionHistory(total=2)

len(x)

5

The same for getVersionHistoryTable and fullVersionHistory method

Version: core-(2.0)
Severity: major
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=72344