pyulog represents char[x] fields as x number of str fields. It seems less surprising to represent them all as one string instead of having to have a postprocess that concats them later. In the docs it's described as a char[127] which would more intuitively map to a string than 127 char values each with their own key (or in this case column).

I've shown an example here but as far as I can tell it impacts all fields that are char[x].

# A logging message, output with PX4_{WARN,ERR,INFO}

uint64 timestamp		# time since system start (microseconds)

uint8 severity # log level (same as in the linux kernel, starting with 0)
char[127] text

uint8 ORB_QUEUE_LENGTH = 4

https://docs.px4.io/main/en/msg_docs/LogMessage.html