2017 Prius 3 heat exchanger bypass?

New to the forums 2017 Toyota Prius 3 owned since new change oil and check fluid levels on regular cadence. I recently crossed the 300k line and started seeing issues so i came and read about a heat exchanger bypass due to the recent issues. White smoke, code P148-F00, and low coolant.

I ordered the gates hose as suggested and installed it. I filled up the coolant and once up to temp topped it off. I allowed it to idle with cap off and topped off multiple times back to full to remove all air from system. I test drove 4 miles and came back and it was at low again. I topped off and allowed it to idle 30 minutes. I test drove again same 4 miles and came back it was at low. I loosened cap to release pressure and noticed it was at full.

The white smoke seems to have subsided. It doesn't smell of antifreeze from the exhaust anymore. It doesn't stutter when transitioning from battery to combustion as it had started to at idle. There's no milky residue in the oil. Generally a blown head gasket you'll remain to see the white smoke on exhaust side, or you'll see the water back up on intake side, or get milky oil.

Can a defective cap build excess pressure on the over flow causing it to not allow water back into overflow? I drive this car 3k miles most weeks and want to ensure I'm safe to do so. Thanks in advance it's still my first hybrid all these years later and I'm still learning.