In fact even deaths under 65 only make up 11% of all COVID-19 deaths.
So again the likelihood of the death rate changing in any significant manner for that specific age group due to the inclusion of the ONS data is currently about zero, for other age groups especially those above the age of 65 there would likely be some changes.
You've neglected to account for the data lag. From your link:
> he information used to produce these statistics is based on details collected when certified deaths are registered with the local registration office. In England and Wales, deaths should be registered within five days of the death occurring, but there are some situations that result in the registration of the death being delayed. For example, when a death needs to be investigated by a coroner. Therefore, there may be some deaths involving COVID-19 that occurred in March and April but are yet to be registered, meaning they will not be included in this analysis.
I'm talking about deaths of young people living in care and nursing homes. All of these deaths need to be investigated by the coroner.
Your assumption is that young people die in care homes is not substantiated by any data we have.
It doesn’t mean that young people don’t die they do even if it’s in extremely rare cases they simply die in hospitals since the current triage grants them priority and that they are less likely to turn to the worse before they can be hospitalized or rehospitalized.
Also unlike (much) older patients they are also not released back to the care homes once they are admitted because they can still be effectively saved.
Overall nothing in the data we have suggests that the death rate will increase for the younger population if anything it will likely decrease slightly as the ONS data skews even higher for the older populations than the PHE data.
So sorry but this is yet again you making assumptions that go directly against the data we have.