Exactly that. Better augmenting existing capabilities or providing low tariff (training/integration) new capabilities. Training, maintenance, spares may sap Ukrainian capacity when they can least afford it.A Leopard 2 is not like a Honda Civic you can just loan out. Tanks require training and support to operate. This is hard to do in the middle of a war (a lesson for those who think defence spending can be put off till a war). The Ukrainians are better off using captured Russian and donated Eastern Bloc kit that they are familiar with and have parts for.
Here explained in detail by retired US 4-star.