I think the tanabe polls the sensor to check for its health, the gauge itself takes several seconds to 'boot' and have a display of the afr's. maybe 10-15 seconds from gauge on to displayI believe you. Never looked at Tanabe gauges
My Prosport and Innovate both say to periodically free air them. Both have the same Bosch sensor you have. But the actual electronics of the systems are different from PLX and I would assume also different than your Tanabe if you don't have to calibrate periodically.