I got a different understanding from that
On p. 72 Suzu comes to the conclusion that for him making the relationship public is not something that has to be done, mostly because he is afraid of a weird reaction 「変な反応」.
Later that page Haruto say that you have to also look at it from the persons perspective that you are telling the secret to.
Now the next page 73 is probably where I’m most shaky, so take this with a grain of salt. I interpreted the start of that page that. If you tell someone else and then tell them to keep it a secret you are pushing the responsibility on someone else.
Later on on that page he goes on to say that you can always tell someone (a secret) but it is much harder to tell someone to forget something.
Next page he goes on to say that he doesn’t want to do anything that would hurt Suzu.
After that Suzu is swooning because he thought Haruto just wanted to keep it a secret because he might be emberassed.
I just interpreted this whole section that both are currently fine with keeping their relationship a secret.
Now as for Tetsu and Mogumo I’m not 100% sure. I don’t think they have reached a conclusion. Though kissing in semi-public might be an indication.