Negotiated Speeds on/off Bridge Mode

[RDLsysadmin01]

So I have a weird issue going on. When I use the bridge mode and add all my ports not being used by WAN I get a negotiated speed of 1000baseTX<full-duplex> but when I use just one port (on the same nic) and delete the bridge then assign that one port as my LAN port, I only get 100baseTX<half-duplex> and I'm perplexed at how the same exact nic, same exact switch and same exact cables can have 2 different speeds...?

Here's my setup:
I have an old Dell Optiplex 5080 with some type of 4 port add on NIC in it. (I don't know the specs of it off the tope of my head). When I have em0, em2, em3 and em4 (em4 is the integrated NIC on the MB but I don't use it because it really is only capable of 100baseTX) added to a bridge and em1 is my WAN port, I can set the LAN interface to use the bridge and I get 1000baseTX<full-duplex> as expected because ifconfig says all the ports on the 4 port card are 1000baseTX<full-duplex> capable.

When I switch it so there is no bridge and em0, em2, em3 are used specifically as the LAN port assignment (individually set of course. Not all at once. I used each one to test separately) I get 100baseTX<half-duplex>..... What the heck...? How can it be 1000baseTX<full-duplex> one way and only negotiate 100baseTX<half-duplex> the other way? How can I tell OPNsense that it needs to negotiate for 1000baseTX<full-duplex> (because it did before on the bridge) and not this limited 100baseTX<half-duplex>?

Thanks for the help in advance.