No, yaySIM does not provide an unlimited data eSIM for Tanzania. The plans listed for Tanzania are fixed data plans, each having a hard data cap of 20 GB.
These plans are valid for a set number of days; for example, the TZ_20_30 plan offers 20 GB for 30 days, and the GL‑120_20_30 plan also gives 20 GB in 30 days but with coverage in many more countries. Choosing a fixed data plan can be more cost‑effective for most travelers, although very heavy data users may need to top up additional credit.