System Information
Operating system: *
Graphics card: *

Blender Version
Broken: Blender 2.93 (after https://developer.blender.org/rBc44c611c6d8c6ae071b48efb5fc07168f18cd17e)
Worked: (newest version of Blender that worked as expected)

Short description of error
This is somewhat rare, but IMO perfectly valid Python use case of dynamically creating a new class and then wanting to register it. That is, we want to dynamically subtype a PropertyGroup class, add some properties to it, and then register the class

One example of "why", is for example MaterialX gives us a whole bunch of shader node types specified in xml files that we would like to create custom node types from, so we write a small script to parse the XML and create node classes on the fly.

Exact steps for others to reproduce the error

import bpy

data = {
             'bl_label': "MyNewType",
             'bl_idname': "test.MyNewType",
             '__annotations__': {
                "MyIntVal": (bpy.props.IntProperty, {'name': "MyIntVal", 'default': 42})
             }
         }

my_new_type = type("MyNewType", (bpy.types.PropertyGroup,), data)

bpy.utils.register_class(my_new_type)

bpy.types.Object.my_prop_grp = bpy.props.PointerProperty(type=my_new_type)
print(bpy.data.objects[0].my_prop_grp.MyIntVal)

also attached a blend file with the above script. In 2.93 does not seem like it registers the int property.