If you are direct to slab then, well, nothing. If your floor was suspended, there could have been a chance of sympathetic resonances moving through the floor to your feet and chair that might have given an overall impression of more fullness when unspiked at the expense of definition. It might have not been a height issue at all. If that were the case I would have recommended actually adding heavy slabs between floor and spikes to bring some definition back. Oh well, that is not the case so don't mind me. I'll just continue lurking.
I am supposedly wood directly over concrete slab...and the floor still acts like a giant soundboard of vibration...in my case with the big sub, I found that isolating everything from the floor...and THEN adjusting the sub gave me all the bass I wanted, along with the tightness which allowed me a clear soundstage. However in the absence of the sub option...I can understand what you are doing. I am guessing of course there is still some reverb coming up off the wood flooring and that it is not solely the proximity to the floor of 1.75 inches or whatever the lack of spikes/diodes equates to in height. Those spikes were designed a long time ago...rumor has it after Martin Colloms did some of his own work on one of the very first Wilsons...and have remained in their design due to its ability to isolate the speakers. So I suspect removing them puts vibration directly in contact with the wood and vice versa.
All guesswork based on my own experiences only.
again, if this is the case, I can see it and get what you are doing, as before I recalibrated the sub and isolated everything, I found I quite liked the sound I was getting with the sub directly on the floor at low sub volumes and having the room fill with fuller bass. when I isolated everything including the sub, I lost all the bass...until I recalibrated my sub...and my sub volume literally went from 8 to 34 and has since increased to 38 with a little further isolation. again, because I lost the floor reverb/reinforcement of the bass when the sub was directly on the floor.