That's also a good point that the Network hardware does not care about cable categories.

If it plugs into your card the card goes "OK, lets see if 1000baseT fits on this?" the cables don't have a little chip or anything saying "I'm not suitable for high speed" the card will figure out whether this looks plausible and just do it.

At the turn of the century I was putting new Cisco gear into a building (which has since burned down, not related) that had been built a long time ago and so it didn't have Cat 5e cables. I was fitting switches which were state of the art at the time (IPv6 experiments), and they didn't have a 100Mbit option because that was legacy, so you'd plug this ancient looking 1980s cable designed for 10baseT into a switch, and in most cases once it's connected the switch and the network card at the far end both go "Aha link, can I do 1000baseT over this?" and conclude yeah, Gigabit just works. There is a setting to say "No, only do 10baseT" but why set it? Users don't want slow Internet.

Unless somebody went very cheap and strung literal bellwire (which was never rated for a telephone but would probably work) or your distances are very long, you will almost certainly get 100Mb and if there actually are four pairs you will most likely get Gigabit.