Eloquent model update method not working through web but working through tinker in Laravel 10.45.1

I have had this problem many times now and I really wonder why this is happening.

Here is its latest occurrence:

public function updateBirthDate(Request $request)
{
    try {
        $request->validate([
            'email' => 'required|email',
            'birthDate' => 'required|date_format:Y-m-d',
        ]);
        $user = User::where('email', $request->email)->first();
        $user->profile()->update(['birth_date' => Carbon::parse($request->birthDate)->timestamp]);
        return response_success([], __FUNCTION__, __('verification.user_data_updated'));
    } catch (Exception $exception) {
        Log::error(__FUNCTION__, compact('exception'));
        return response_error(__FUNCTION__, $exception->getMessage());
    }
}

The code above didn't change 'birth_date' in database when I sent the request through Postman.

But when I ran the line below in tinker, it changed 'birth_date' in database:

$user->profile()->update(['birth_date' => Carbon::parse('1990-01-01')->timestamp]);

I suppose this is a bug in this Laravel version.

I have noticed the reason when one of my methods with update didn't work but another one worked.

The following didn't work:

$user->update([
    'confirmation_code' => random_int(100000, 999999),
    'email' => $request->email,
]);

The following worked:

$user->update([
    'mail_confirmation' => true
]);

I have missed a basic point.

The second one works because 'mail_confirmation' field is in $fillable array but first one doesn't work because 'confirmation_code' isn't in $fillable array.

Update is one of the mass assignment methods of Laravel Eloquent ORM Model. Others are fill and create: https://laravel.com/docs/10.x/eloquent#allowing-mass-assignment

So, all the fields must be in $fillable array unless $guarded array is set.