Hi
I would consider they do, so ISP provided router would give advertised speed as tested from router to ISP termination point. However, the firewall would be basic and in supplied mode, only contain a couple of rules. This to me though is similar to the connected speed of ADSL/FTTC as that is not the speed you would have but the connected speed.
However, please note the minimum guaranteed speeds - using 500/70 package from BT
Average
501
Mbps
Download
Average
68
Mbps
Upload
Minimum guaranteed speed: 250 Mbps download
Also, you would need good equipment/computer to use that speed, anything low powered would not be able to handle the throughput @500mb/s
The Draytek G3uiss posted (2927) is rated performance at 1000 mb/s at firewall I believe.
I do not understand why you are looking for exact speed at those speed throughputs... do you complain over your car consumption to advertised car consumption or your fridge or washer using exact power as advertised...
Also, I guess not many realise but John posted that FTTP is not as reliable as FTTC and I concur, it is not (see picture wan 1 BT FTTP 900/900 wan 2 FTTC 80/20). I also noticed recently that BT state 48 Hours to fix and I cannot see the 900/900 package anymore
48 hour resolution
We will aim to fix your fault by the end of the second working day after you’ve told us about the fault.
Please do not think I am having a go, it's just something I do not understand with people so not trying to upset anyone
Many thanks
John