As far as I understand, haematocrit is red cell volume. So if your haematocrit is 44%, all that you can deduce is that other cells make up 56%, however this 56% will be made up of more than just white cells, it’ll contain clotting factors too. You can have a blood test that counts white cells, there are 5 types, neutrophils, lymphocytes, monocytes, eosinophils and basophils.
Haematocrit is also known as packed cell volume (PCV). It's the volume of all the blood cells as a percentage of the total volume of the blood (the rest is plasma). As the majority of blood cells are red cells, it's sometimes described as a measure of red cell volume. https://labtestsonline.org.uk/tests/pcv