If one were in a charitable mood, one could think of this as a "just in case" measure of ongoing capability assurance in the event of a broader conflict. In a less charitable mood, one might imagine it as preparation for proactive action. In either case, if you don't do this kind of sub-threshold stuff at least occasionally, you often discover that when a real conflict erupts, the capabilities you thought you had are in fact literally or figuratively rusty. (See the Russian army's logistical debacle early in the Ukraine war for a recent example.)
Most top tier nation states do some version of this; each one has its own style. The Russians are somewhat unusual in that they care less than most who knows or suspects them of this kind of activity.