My impression in the original was that Aerith wasn't a high priority at the time, and since Tseng obviously has a thing for her, he gave her some leeway and nobody up the ladder complained. When they crashed Sector 7, the president renewed the plans to obtain the Promised Land, so Aerith became a priority again and they kidnapped her. In FF7R, the implication seems to be more that they played nice because from their perspective, the best way to get the information is to win her over ("she has to come willingly"), but when they destroyed Sector 7 obtaining the knowledge became more urgent so they switched to more drastic measures. Basically the same idea, just differently flavoured.