MongoDB Timeseries Schema results in bytes in buckets collection

I have a local MongoDB 6.0.3 instance running on Docker. I created a DB with a time series collection with time field timestamp and meta field nodeId. My test data was written to multiple files, which I then wanted to migrate to MongoDB with Python. Every file contains json records sampled at 500 ms and each file contains about 1.5k records (so 1.5k of documents as shown below are inserted at the same time).
Data is inserted with the following schema (approximately):

{
    timestamp: 2022-11-22T0552:11.235,
    nodeId (meta field): "myNode",
    sensorsArea1: 
        {
            sensor1:
                {
                    value: 23.3,
                    unit: "°C"
                },
            sensor2:
                {
                    value: 5000,
                    unit: "rpm"
                }     
        },
    sensorsArea2:
        {
            sensor1:
                {
                    value: 523.2,
                    unit: "mm"
                },
            sensor2:
                {
                    value: 8,
                    unit: "-"
                }     
        },
}

In the buckets collection it looks something like this:

{
    _id: ObjectId(),
    control: {...},
    meta: "myNode",
    data:
        {
            timestamp: byte[44] (Unknown 0x07),
            sensorsArea1: byte[2171] (Unknown 0x07),
            sensorsArea2: byte[3690] (Unknown 0x07)          
        }
}

The fields in the nested document data are of type Binary - Unknown 0x07. But I would expect a list of values at each sensor in the different sensor areas.

Question 1: Is the schema of my insert suitable for a time series collection?
Question 2: Is my expectation correct concerning the resulting schema in the buckets collection?