I am just guessing but Tampa probably didnt see the higher skill at LT. You cant fault someone because another owner doesnt see the difference, a higher pass blocking will get a better rating on the left side just like a higher run blocking will produce a higher rating on the right side. I do the same when drafting, looking for FA's or deciding on trades.
Also if you set your player weights the same for both sides then you wouldnt see any difference. I believe the generic setting is like 100/25 pass/run block for LT and just the opposite for RT