You can draw that contrast (increasing vs strictly increasing), but what I was taught was to contrast increasing functions/sequences with nondecreasing functions/sequences.

A book or paper will make it clear what they mean by "increasing" by using the definition. There, it doesn't matter at all -- they could just as easily coin new words, since they immediately give the full definition. But the people hanging around this thread, telling people who are using a very common definition of "monotonically increasing" that (in paraphrase) "I hate to be pedantic, but you've made a mistake, in that I would have phrased that differently" have failed to contribute anything or to be pedantically correct. There's no case to be made that, if I say a "monotonically increasing sequence" must be increasing rather than nondecreasing, I've made a terminological mistake. This is a term with different definitions in different treatments.