Understanding Wireshark: Are these Phantom Packets or normal I/O artefacts on I/O Graph Wireshark

Question

As the title states, I need some clarification on the appearance of small spikes in my I/O Graph that do not correlate with any packets.

As seen in the screenshot, when attending to these spikes in the I/O graph with the cursor wireshark notes that there are no corresponding packets for that point.

Just want to know what this behavior is and whether these are just expected artifacts or perhaps caused by not having a small enough time interval etc to observe them. I assumed it to be previous frames that are in transmission, but all the neighboring spikes (that also have no corresponding packets) have a large time interval between them.

For further context this capture session is monitoring a direct net facing Ethernet connection traffic and so any and all applications and services using the internet are being monitored