How can I change the tip_width and tip_height of NumberLine? (manim v0.15.2)

(Hi. This is my very first question on stack overflow so please let me know if the question is unclear.)

I am trying to make the arrowhead of a NumberLine mobject smaller than its default (which is tip_width = 0.25, tip_height = 0.25). However the tip customization doesn't seem to be working. Here is the code and the result:

from manim import *

class NumberLineComparison(Scene):
  def construct(self):

    l0 = NumberLine(
      x_range=[-3,3],
      include_tip=True
    )

    l1 = NumberLine(
      x_range=[-3,3],
      include_tip=True,
      tip_width=0.1
    ).next_to(l0,DOWN)
    
    l2 = NumberLine(
      x_range=[-3,3],
      include_tip=True,
      tip_height=0.1
    ).next_to(l1,DOWN)

    self.add(l0,l1,l2)

Resulting Image

The changes in tip_width and tip_height attributes don't seem to be active...

Is this a bug or are there any problems with the syntax?