Literally all the time. Just had exactly this scenario with a technology switch. I spent an hour reviewing their api. We had a meeting with their sales engin

Literally all the time. Just had exactly this scenario with a technology switch. I spent an hour reviewing their api. We had a meeting with their sales engineer, I asked them a bunch of questions. Estimated 10-12 days to finish phase one integration, was working in single sprint. Larger projects get more upfront investigation and larger error ranges.