It's a technical limitation, not a set speed limit
This is pretty much normal. Accoring to this link, DSL is optimized more on downloads than uploads because most users spend time downloading than uploading (eg. loading sites, downloading files) and DSL is pretty much a slow tech relying on copper cables. Then we have other factors such as your wiring, modem, ISP themselves.
Hence, you should get Fiber plan. Both guaranteed up to advertised ups and down. Either PLDT or Converge. Both offer the same service anyway since
But if I would recommend, get Converge cuz I think their GPON routers are better. PLDT’s GPON router is utter shit, can’t change my DNS and they even turned on AP Isolation by default with no option to turn it off.