Oh, and another thing about Gero's abilities: He HAD data from Freeza's cyborg form, and had 3 years to use that and improve his androids. 19 and 20 were not stronger than Super Saiyans, so they weren't stronger than Freeza, and it's specifically said 18 and 17 were too strong and rebellious to be used.
This is likely why the main timeline Androids were stronger. Remember that in the Alternate future, the Androids were crueler, but weaker. Trunks / Gohan could go one on one with them for a while.
So it actually makes sense that in the 3 years of using Cyborg Freeza's data that he could adapt and improve. If the Briefs family could reverse engineer Namek tech, why couldn't Gero with Freeza tech?
So that Freezer could be as strong as possible when he cyborged up. Unless they made Mecha Freezer gimped on purpose.
Freeza was floating in space, dying and bleeding and missing 2/3 of his body. They had to get him back together with what they had. They probably worked as fast as they could.
Gero had 20 years to slowly work and perfect his designs.