The film heavily suggests that the only way to go back to the future coming from the past is through the platform. I’m pretty sure even Russos said as much in an interview. The time travel - if it happened, I throughly don’t believe it did, this is old Cap living in the MCU timeline - happened with Cap and he didn’t go back through the platform, so of course if it ever did happen like the Russos say, it happened through his perspective.Sorta like how you are creating holes for the Russo's with this
"Once Cap - even from minutes after - goes back to the "main" timeline, he is also creating an alternate future because, from his perspective, even through an alternate reality, that moment happened in the past, since that would be the only way he would be able to use the time travel gps: only to go back further in time, not really the other way around."
The movie NEVER suggests it's about Caps perspective. It's about whether the act time travel is changing the past. If he travels to the present of a timeline, he isn't changing its past - even if this timelines date is chronologically earlier than the date he left from.
So by their own rules - that I disagree with - Cap going back to the past creates an alternate future... in 2023 as well.