Flipping Apostate

Just finished a long slog with Apostate, my first time facing him to be honest, and I ran into a little confusion with his flip condition.

On his first side, if he drops to 0 hp he destroys a relic, flips, and gains 20 hp. Then, if he would be dropped to 0 on his second side he would destroy a relic and flip. At this point though, his hp remains the same correct? so if he had 2 hp left he would still have 2 hp left, but if he had a third relic and I hit him again he would flip and go back to 20. Does this sound correct?

I almost had this happen (Char destroyed the third relic and finished off Apostate thanks to a massive turn by team Tachyon/Tempest/Scholar) and I just want to make sure I would have played it properly