You're mixing up logical and extended partitions. Go and read about PC partition structure.
You can have up to 4 primary-or-extended partitions, and at most one of it may be extended¹. An extended partition is a container for logical partitions¹. A primary partition or a logical partition is a container for a filesystem (or an LVM volume or some swap space or a BSD partition or other kind of volume that isn't a PC-style partition). The swap partition is nested in the extended partition because that's what it means to be a logical partition.
In your case, making the swap partition a logical partition rather than a primary partition won't change anything regarding the primary partition quota, since you don't otherwise have an extended partition. If you wanted to free one primary partition slot, you'd need to have at most two primary partitions in addition to one extended partition.
Note that Linux doesn't care whether it's installed on primary or logical partitions. You could make both your system partition and your swap partition logical. Or you could create one partition that's an LVM physical volume and create two LVM logical volumes, one for the root filesystem and one for swap. LVM gives you easier management within Linux at the expense of other OSes seeing the LVM physical volume as an opaque blob.
¹ That's not strictly required, but you'd have to go through hoops to circumvent that, and your fellow administrators will curse you.