Python file write() stuck in append mode when read() has byte count as parameter

Why do these two very similar codes behave so differently?

Code 1:

with open("new.txt", 'w+') as f:
    f.write("this is a line")

with open("new.txt", 'r+') as f:
    f.write("***")
    f.read()  # << note here
    f.seek(0)
    print(f.read())

Output: ***s is a line

Code 2:

with open("new.txt", 'w+') as f:
    f.write("this is a line")

with open("new.txt", 'r+') as f:
    f.write("***")
    f.read(1)  # << note here
    f.seek(0)
    print(f.read())

Output: this is a line***

Python version: Python 3.10.6 (tags/v3.10.6:9c7b4bd, Aug 1 2022, 21:53:49) [MSC v.1932 64 bit (AMD64)] on win32