It's remotely possible but highly unlikely.
Your max attainable is only just over 44Mbps so after overheads you'll only be able to squeeze an extra couple on Mb any way, totally unnoticable.
Have to agree, you will notice absolutely no difference between 40M and 44M.
Agree the sync does vary a bit but it's the IP Profile that never changes has been fixed at 38.67 for nearly eighteen months, no variation at all since the initial 10 days when was finding limit, hit max I was then paying for and has stopped there.
Dispite now min going up to 55/10.
I suspect it is just the max attain sync rate that is varying not your actual sync rate. If the actual sync rate doesn't vary neither will your IP profile. Your IP profile is calculated as 96.69% of your sync speed.
I tried calling today, sorry I missed you. I've been in touch with wholesale about this and they've advised on sending an engineer to check it for you. I'll be in the office tomorrow so I'll call again to organise that if it suits.