This is not true at all. MagSafe is useful for convenience, not charging speeds. All iPhone models are capped at 15W charging via MagSafe wireless charging (assuming you used at least a 20W charging brick). If you use wired charging, you'll get the full 20W charging rate from your 20W charging brick.

Apple's own MagSafe battery pack tops out at 7.5W when charging on-the-go, primarily due to heat concerns. You only get 15W when the battery pack is plugged into a power outlet that's at least 20W. If you go wired, plenty of battery packs off Amazon will offer you 10W+ for very cheap.

TL;DR: MagSafe is for convenience. It is not faster than wired charging.

Same for me. I can see this being more useful for people who don't typically carry around handbags/satchels. If you are, though, there's just no advantage to carrying a battery-powered wireless charger: just go wired. It's much faster, generates minimal heat, and can top your phone off multiple times (depending on your battery pack).

Same reason why I use wired charging in my car, even though it has wireless charging available. I'd... rather not have my phone get hot to the touch from wireless charging + the sun beaming into my car, especially if wireless CarPlay is active. Wired will charge it faster and be cooler, so what's the point?