All location recording apps on iPhone must be alive (ie not swiped closed) in order to record location. iOS does not store any location data for later retrieval, so if an app is not alive at the time, it gets no location data and can’t fill in that gap.
Arc (and other apps) can partially get around being swiped closed by using various tricks to get automatically relaunched in the background. But there will be always be minutes or hours of delay between the app being swiped closed and the app being automatically relaunched, during which time there will be a gap in the location data.
The other apps you mention mostly don’t record constant location data, instead relying on only periodic “significant location change” location updates, which are typically 15 minutes or longer apart, and often hours apart. Gyroscope does attempt to do constant location data recording, which means it suffers the same as Arc when swiped closed, and either has to hope for a quick auto relaunch or has to fudge the data in the UI and hope you don’t notice the gap.
Most location recording apps intentionally rely only on location data with significant gaps between samples (minutes or even hours), and present the data in their UIs in such a way as to gloss over the gaps. Arc however is designed to record the highest detail, and doesn’t attempt to fake over any gaps (with the exception of gaps within a single visit, such that the gap started after arriving and ended before leaving).
So in short: Don’t swipe the app closed. And as a general rule of thumb, don’t swipe any apps closed. On average it won’t save you any battery, and in fact will end up costing you more battery life.
When you swipe an app closed, and it is then automatically relaunched (or relaunched manually by you) the app has to repeat its energy expensive launch cycle each time. By swiping apps closed from the app switcher, typically you will be shortening your phone’s battery life each day rather than extending it.
Instead if apps are left alone in the background, they will either go into a fully suspended state where they consume no energy at all, or will quietly do their work in the background while consuming very little energy. Then when the app is brought back into the foreground it doesn’t incur a repeat of its energy expensive launch time processes.
The most energy consuming part of any app is its time in the foreground, powering the screen’s brightness, and using energy to update its UI. When apps are in the background they consume orders or magnitude less energy. In Arc’s case, a few minutes of foreground time consumes about the same amount of energy as several hours of background recording.
If Arc is left in the background, it can continue recording for 24+ hours on a single charge, and on larger/newer phone models possibly can even beat 48 hours of constant recording on a single battery charge.
Anyway, either way, if you swipe the app closed you will get data gaps, and the same is true for all location recording apps.