No disrespect intended, but that's not necessarily an "oops" in my opinion, but rather it may be intentionally built in good design from days gone by. I believe in the old days the sewing across the top of the strap was done on purpose for sure, but not to get extra return business, I honestly never heard that one before and it didn't start with me. Over time it seems most straps will fail where sewn to the pouch from rot and wear no matter how they are sewn on. A repair to a strap sewn across the top is easy and can be done in a few minutes with no damage to the pouch. If a perpendicularly sewn strap fails it seems like it often tears the back of the bag too, making repairs very difficult at best. At least this is what I have observed when restoring old bags, and even mending a few new ones.
Now many of us today may not use our bags enough to observe this, but some still do and as mentioned I have repaired some of those bags for them when the strap fails. This work is actually some of what caused me to start thinking along these lines to begin with. To me its kind of like engineering in a shear pin on machinery gears or pulleys so you don't destroy everything if there's a failure. It seemed funny that I may be ignoring original designs and what it may be telling me on leather work like this but I'd strive to copy every minute detail on other artifacts. For myself, I'm afraid I could really miss understanding something important with generalities like saying sewing across the top just isn't a good way to do it. That would never help me to understand why they did.
It kind of reminds me of the guys that not too long ago said you should never pin or glue in a powder horn end plug because it makes a grenade. Anyway, these are just my own observations and ideas on strap attachment and why some of the old time makers did what they did. Not all of them sewed across the top by any means and some attachments were quite creative, so of course in the end, to each their own. And most importantly, again, I mean no offense or disrespect to anyone's opinions on this topic, and thanks for indulging my ramblings.
TC