two way DataBinding not working properly in viewholder

So I have a viewHolder with a checkbox here is my viewModel

@Bindable
var itemIsSelected: Boolean = isSelected
    set(value) {
        if (field != value) {
            field = value
            notifyPropertyChanged(BR.itemIsSelected) // this doesn't work
            notifyChange() // this one works
        }
    }

here is my viewHolder class

inner class SpecialityItemViewHolder(val binding: ItemSpecialityFilterBinding): RecyclerView.ViewHolder(binding.root) {
        fun bind(specialityItemViewModel: SpecialityItemViewModel) {
            binding.viewModel = specialityItemViewModel
            binding.executePendingBindings()
            this.itemView.setOnClickListener {
                binding.viewModel?.let {
                    it.itemIsSelected = !it.itemIsSelected // this doesn't trigger ui changes
                }
            }
        }
    }

xml

<?xml version="1.0" encoding="utf-8"?>
<layout>
    <data>
        <variable
            name="viewModel"
            type="packagename.ItemViewModel" />
    </data>

    <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/vertical_margin_small"
        android:paddingBottom="@dimen/vertical_margin_small"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools">

        <Checkbox
            android:id="@+id/checkbox"
            android:layout_width="25dp"
            android:layout_height="25dp"
            android:checked="@={viewModel.itemIsSelected}"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"/>

    </android.support.constraint.ConstraintLayout>
</layout>

so what happens is that the setting is working properly as in that when i press the checkbox it sets the backing field to the corresponding value but when i set the backing field (notice code in bind function) it doesn't trigger ui change I know that calling binding.executePendingBindings() would solve the problem but my understanding is that notifyPropertyChanged(BR.itemIsSelected) should not need executePendingBindings call, Actually if i call notifyChange instead everything works properly ( but I presume there is performance issue here as it notifies change for all properties instead )

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