But it’s surprising how poor the reliability can be. Aside from your points, solder can wick up a cable, and then the cable often breaks just at the point where the solder ends since it has no strain relief and may be right in the middle of a bend. This is especially true for adding solder to a crimped connector “for good measure”. It does more harm than good.
That being said it’s convenient many times especially if you don’t have connectors on hand or need to place wires in a specific orientation. Hot glue or better yet, RTV silicone can be used to make strain relief to increase the reliability. Or, when using perf board like in the post, a good technique is to drill a hole for a snug fit of the cable including insulation, then pass the cable through the hole before soldering to an adjacent hole.