Can't tell from the story that the hospitalizations were related to COVID-19, only that the children tested positive and were admitted for unspecified reasons, during the two time periods when each variant Delta/Omicron was dominant.
And about 81 percent of hospitalized children were admitted primarily for COVID-19, compared with about 82 percent during the omicron wave.
The study itself says:
No significant difference was detected between the Delta- and Omicron-predominant periods in the proportion of patients with COVID-19–related symptoms recorded at admission (87.7% versus 86.9%) or with COVID-19 as the primary reason for admission (81.3% versus 81.6%).
That's the point.
If we follow NY's recent disclosures though, virtually all were incident, not the cause.