It’s interesting that Preston vomited as soon as JV got to his mums to pick him up and JV took him home covered in sick rather than change his clothes quickly at his Mum’s. Perhaps he did a lot to keep some of the more obvious injuries from her. His bottom may have recovered enough to look like a more average “sore bum” presentation and less startling by the time he took him round after the cot incident.
He was also always playing the worried new Dad around family members which served two purposes- made him look like a doting father and began to form a picture of a frequently poorly “difficult” baby that suffered from seizures, chest infections, his life threatening squint

Can probably add a third motivation too - lots of poor Jamie attention and drama.
A big dose of speculation and arm chair psychology here but I also think that seeking their help and advice (sleep trainer sister too) it massages the ego a little bit. Oh look they need me again, I can help, they’re so inexperienced.. I think that means you don’t lead with suspicion and intrigue.