You know the ones… Joeblow booster, Bonty flash charger, Lezyne pressure overdrive.

When topping up a tyre, do they all inflate through the reservoir, therefore equalising the tyre pressure into the chamber?

When I had a quick look at them, I couldn’t find any that could function as a normal track pump, an airshot style inflator, or both

They all seemed slightly compromised…

But I didn’t spend a huge amount of time looking

As I thought.

I’ve got the Airwave one.

Its got a valve on the pump head. The settings are “Pump” and “Tank”

On pump it works like a normal pump (the gauge goes up to 240 psi though so its not the best for accurately sticking 20 odd psi in MTB tyres).

Flick it to tank and it fills the reservoir. Flick it back to pump to dump all the air into the tyre.

It might be equalising the air between the reservoir and the tyre in normal pump mode but it doesn’t seem to have any effect on how it works as an ordinary track pump (other than the gauge no being very useful)

I have a flash

It does work as both (but yes you need to pump the ‘tank’ and the tyre)

or
connect to tyre valve
flip air lock on
pump tank to Xpsi
open airlock
pump to adjust tyre/tank psi to correct
flip airlock on
move to next tyre without losing tank pressure
repeat etc
no idea how accurate the guage is