I had similar concerns. I'm not sure what qualifies as "extensive travel" considering it was practically impossible to travel outside of Canada for two years (20-21), but I had a combined total of 116 days outside of Canada; five trips to the US and the rest to ~12 other countries. Let's say 12 unique departures from Canada and a total of ~14 unique countries covered. (I diligently listed all the countries.)
I was lucky to not require a PCC for any of them, nor was I asked for passport scans. I cross-checked my entries and exits in and out of the US against I-94 data and was correct, but the same information and detail was not present in my CBSA notes -- some departures (and arrivals?) were simply missing. This meant that I was more than half expecting to be asked for passport scans because I fell so close to 1,095 days (1,102 days present).
@Dr. Walden chimed in on one of my posts pointing out that some flight and road departures to the US pre-2019 (?) were not available to CBSA, and this was a plausible trigger for passport scans. (The great irony being that I-94 is in the public domain and CBSA/IRCC don't simply verify this information themselves!)
Anyhow, getting to your question, I conclude, like all things with IRCC, nothing makes sense because I was not requested for passport scans (and I am very glad I didn't send them in preemptively based on
@shiremag's advice). Why one is asked for passport scans while another with a comparable travel history isn't beats me: Perhaps it is down to the overall candidate profile? But it's more likely down to individual officer discretion.
EDIT: Adding the fact that when I applied for my PR Express Entry in 2018, I had a wild number of international trips, something like 140 in the 10 years prior. I worked a job in the UK that required frequent travel to the Schengen Area (and thankfully the EU stamps both on arrival and departure). I'm speculating that maybe they were conditioned to the fact that I am known to have an extensive travel history and they shouldn't have expected any different for my citizenship application?