Not 100% sure about how Fibe works, but I'm assuming it is still PPPoE. That protocol has overhead which takes away from the speed you "see". The information is sent in "envelopes" and at your end the "envelopes" are opened and data you use taken out. The "envelopes" are still part of the mail volume, but useless to the receiver. A 5 Mbps connection will top out around 4.3 Mbps so it makes sense that a profile set at 7 Mbps tops out somewhere around 6 Mpbs measured speed.
I have heard Bell has set higher speed offerings at higher speeds so that end users get the full speed advertised (i.e. 28 Mbps for 25 Mbps service so when the user speed tests it they get 25 Mbps)
I have heard Bell has set higher speed offerings at higher speeds so that end users get the full speed advertised (i.e. 28 Mbps for 25 Mbps service so when the user speed tests it they get 25 Mbps)