You could do something with toscalar() values and the like, would something like this work in your use case?

let AzureMetric = datatable(timestamp:datetime, metric:string) [
datetime(2024-10-28 12:00:00), 'metric1',
datetime(2024-10-28 15:00:00), 'metric2'
];
let AegDataplaneRequest = datatable(timedate:datetime, request:string) [
datetime(2024-10-27 12:01:00), 'request1',
datetime(2024-10-28 13:01:00), 'request2'
];
let MostRecentAzureMetric = toscalar(AzureMetric | summarize max(timestamp));
let MostRecentAegDataplaneRequest = toscalar(AegDataplaneRequest | summarize max(timedate));
let TimeDifference = datetime_diff('minute', MostRecentAzureMetric, MostRecentAegDataplaneRequest);
print TimeDifference