I think that's just an excuse to not spend more. Why is China still the second most powerful military when they can be first with their 40 trillion GDP PPP? Why not boost up their number of planes, missiles, carriers? The fact is China is showing too much restraint and will suffer for it in the future.
Weapons quickly become obsolete, especially today with such rapid development of military technology. If I arm myself massively today, I may have obsolete weapons tomorrow. Therefore, it is necessary to estimate the time of the future conflict well. It must not happen that the enemy will catch us at the moment of rearmament. This happened to the USSR at the moment of the German attack. They had a lot of aircraft, but they were obsolete and new ones had only just begun to be produced. The same goes for tanks. Such situations must be avoided by wise leadership.
By the way, 1.5% is not so little. Moreover, what is saved on rearmament can be invested in factories and research. These can then be involved in armaments at any time.