What you say is not true of everyone who meets the DSM-5 diagnostic criteria for ASD–"meltdowns", or "what, why and how fast makes you feel overwhelmed" are not part of those criteria–so it is possible to have ASD (per DSM-5) yet not have those symptoms, and indeed there are people out there just like that.
Conversely, there are people for whom what you say is very true, but who don't meet the diagnostic criteria for DSM-5 ASD, and hence officially don't "have autism". People with anxiety disorders, panic disorder, OCD, etc, can have very similar (if not identical) experiences, yet they don't have the right set of other symptoms to meet the DSM-5 criteria for ASD.
I get the impression you are defining "autism" anecdotally, based on your own personal experiences and those of others you know, or based on popular information sources (as opposed to the research literature). When you define it that way, you may actually be talking about a rather different construct from what the DSM-5 is talking about.
Conversely, there are people for whom what you say is very true, but who don't meet the diagnostic criteria for DSM-5 ASD, and hence officially don't "have autism". People with anxiety disorders, panic disorder, OCD, etc, can have very similar (if not identical) experiences, yet they don't have the right set of other symptoms to meet the DSM-5 criteria for ASD.
I get the impression you are defining "autism" anecdotally, based on your own personal experiences and those of others you know, or based on popular information sources (as opposed to the research literature). When you define it that way, you may actually be talking about a rather different construct from what the DSM-5 is talking about.