Regression in pretty-printing diff in ExUnit

[fuelen]

Elixir and Erlang/OTP versions

erlang 26.0.2
elixir 1.15.4-otp-26

Operating system

Linux

Current behavior

defmodule MyTest do
  use ExUnit.Case, async: true

  defmodule MyStruct do
    @derive {Inspect, only: []}

    defstruct [:callback_fn]
  end

  test "compare" do
    assert %MyStruct{callback_fn: &String.to_atom/1} == %MyStruct{callback_fn: &String.unknown/1}
  end
end

output with elixir 1.15.4-otp-26: left and right are equal

  1) test compare (MyTest)
     test/my_test.exs:10
     Assertion with == failed
     code:  assert %MyStruct{callback_fn: &String.to_atom/1} == %MyStruct{callback_fn: &String.unknown/1}
     left:  #MyTest.MyStruct<...>
     right: #MyTest.MyStruct<...>
     stacktrace:
       test/my_test.exs:11: (test)

output with elixir 1.14.5-otp-25: left and right are different, diff highlighting is present

  1) test compare (MyTest)
     test/my_test.exs:10
     Assertion with == failed
     code:  assert %MyStruct{callback_fn: &String.to_atom/1} == %MyStruct{callback_fn: &String.unknown/1}
     left:  %MyTest.MyStruct{callback_fn: &String.to_atom/1}
     right: %MyTest.MyStruct{callback_fn: &String.unknown/1}
     stacktrace:
       test/my_test.exs:11: (test)

if I remove @derive {Inspect, only: []} then with elixir 1.15.4-otp-26 output is the same as with 1.14.5-otp-25 but without diff highlighting.

Expected behavior

behaviour from previous version