Not really. There is only a Switch with GBit and standard FritzBox 7590 as a Router. The Switch is connected to the Router on the WAN Port as it should be (if i remember right) and the RPi4 to one of the Switch ports. The Laptop is directly connected to the router. The cable is a standard GBit cable. There should be nothing with 100MBit.

The speed looks fine for me on the Laptop itself:

/dev/sda:
 Timing cached reads:   28080 MB in  1.98 seconds = 14161.28 MB/sec
 Timing buffered disk reads: 448 MB in  3.02 seconds = 148.55 MB/sec

 /dev/sda:
 Timing O_DIRECT cached reads:   604 MB in  2.00 seconds = 301.42 MB/sec
 Timing O_DIRECT disk reads: 454 MB in  3.02 seconds = 150.36 MB/sec

On the Pi itself i get:

/dev/sda:
 Timing cached reads:   1974 MB in  2.00 seconds = 988.54 MB/sec
 Timing buffered disk reads: 196 MB in  3.02 seconds =  64.91 MB/sec

/dev/sda:
 Timing O_DIRECT cached reads:   122 MB in  2.01 seconds =  60.64 MB/sec
 Timing O_DIRECT disk reads: 194 MB in  3.03 seconds =  64.03 MB/sec

This also much above the speed, i got, when i transfer files via SFTP/SCP.

I have tested also iperf and got: 0.0000-10.2100 sec 113 MBytes 93.1 Mbits/sec

It seems like this is really somewhere limiting to 100MBit.