Why would you delete the app? We know that authorities can’t connect you to the request to isolate since the app holds no personal data. So the choice to self isolate is yours. Even if you chose not to isolate it’s a useful ping, you may chose to avoid elderly relatives, do flow testing… Your friend with the calls from T&T this cannot be as a result of the app.
The rumour I've heard is that they haven't got enough stocks of Pfizer to meet demand in the under 30s (.9m doses until September for ~20m people) so are wanting to get immunity in the young through infection. The same reason that the UK aren't vaccinating teenagers while many other countries are (it also allows them to declare themselves winners of the vaccination race by ending it early!). Today also gives cover with schools shut for six weeks, so any impact might not be as bad as it would have been with the kids in school (slower rise in cases, hospital admissions, etc). If the cases don't climb significantly (see Holland, Denmark, Israel, etc), then they can blame something else if it goes wrong later. Ending sanctions early might have caused problems with the football authorities over the Euro's finals too - and it appears we have at least a couple of cases on this thread resulting from the final at Wembley.