By "violate" I assume you mean ducking under the glideslope on short final to make the view out the front seem more normal - which is of course very tempting.
Your operating procedures may be different, but our SVref (steep Vref) is faster than normal Vref. When we arrive over the threshold at LCY we flare lower, but more aggressively, than on a normal arrival. In our aircraft this "firm pull" bleeds off a lot of energy quickly - I can also confirm from experience that if it's mis-timed even slightly, the stick shaker will clatter as we touch down.
The general result is a firm arrival with a nice short landing roll.
My understanding is that if you duck under the glideslope to achieve a normal profile in the last portion of descent, the flare and touchdown will be more "normal", but you'd better flick over to the normal landing distance tables, rather than the steep approach ones.
Glancing at our Ops manual, I can tell you that at a typical heavy-ish landing weight, the factored landing distance for a 5.5 degree "firm" arrival, on SVref, sea level, ISA, no wind, would be 3740 feet. Same conditions, for a normal 3 degree "smooth" arrival, on Vref, factored distance would be 4350. Bearing in mind that SVref is actually 5 knots faster than the corresponding Vref, the duck-and-smooth-it-out strategy could actually take somewhat more distance than that.
So the short answer is - yes, ducking under will extend the landing run and invalidate the landing performance data.