Cause decreasing the load time with 10% is quite dramatic when in SEO terms
Hi Bendict.
Page speed is far from so dramatic as you assume. This is one of the non-very significant factors when ranking. Besides, Google Page Speed and other services are very subjective. They can easily be deceived without resorting to real performance improvements.
As for lower speed when using a page builder (any, not only SP) it is the expected behavior and fee for the possibility of visual editing. Any Page Builder carries on board a lot of code that is required for its work. If you are not ready to pay this price, do not use page builders at all. Use the source code instead.
By the way, SP Page Builder is one of the fastest among other page builders. But of course it does not compare in speed with a clean code.