They are somewhat alike in terms of nominal composition values. That one aspect of a steel. Others are purity and microstructure and here it's a difference between the two.
If a knife is used very lightly, always cleaned and touched up after the light usage it would be little difference between a spring steel and a knife steel. Only in hard use will the differences between steels really show.
Things like toughness, resistance to microchipping, re-sharpenablity, edge stability and wear resistance.
When you deform your edge on the strop, how does that happen? Are both knives equally sharp? Same angle? Have you checked for microchipping? Some steels tend to chip instead of roll, hence you will see no "deformity" on your strop. A coarse grain steel like 8CR13MOV should have a stronger tendency to microchip then 13C26. If it chips, it will not roll (deform). An edge needs to be sharp and narrow to roll. If it's course and have a wide edge angle that will not happen, and the knife will not "gain any sharpness" from stropping.