Warden of the Grove causes non-token creatures to endure X when they enter, where X is the number of counters on Warden. However, when Warden's trigger goes off (when the player chooses which endure option the creature entering will take), the text is incorrect if warden has not been affected by another source up to that point.

Specifically, the text for the Endure option where the creature gets X +1/+1 counters has {CardName} instead of the actual name of the creature getting the counters. (This is shown in one of the screenshots)

However, if Warden has had counters (at least, +1/+1 counters) added to it by another source, such as Ornery Tumblewagg, Good-fortune Unicorn, or Sylvan Scavenging, then the Endure option for adding X +1/+1 counters correctly substitutes the creatures name in.

Note in the screenshot where Warden has {CardName}, Warden has had its counters affected by the two Kami of the Whispered Hopes in play and the fully leveled up Innkeeper's Talent. This means that "passive" effects (I've heard of replacement affects, but I'm unsure of which would be considered replacement or not so I will just use passive to cover the ones I can see on screen) do not cause the issue to go away.

Once Warden has had counters added to it by another source, it correctly displays the name of the creature in the text instead of {CardName}.

There is at least one caveat to this: (I do not want to test every possible combination to add counters to Warden and did not, so there could be other edge cases as well)
- If Innkeeper's talent was used to add counters to Warden, the {CardName} issue persisted. In the game the screenshots came from, I used Sylvan Scavenging's end of turn trigger to add a +1/+1 counter to Warden, and from then on the text displayed correctly.
-- For the above: I also know that if a creature affect caused Warden to gain counters, then the +1/+1 counter Endure affect from Warden works as expected; So, I'm not certain what exact affects cause Warden's text to write correctly vs incorrectly
- Another caveat is I've only tested this with +1/+1 counters; I have not tested with other kinds of counters

tldr; If Warden of the Grove has not had +1/+1 counters added to it by another source, it's Endure affect to add +1/+1 counters displays {CardName} instead of the creature's name

The screenshots
- Warden incorrect text: Shows the issue when Warden has not been affected by another source yet when its trigger goes off, specifically on a third Kami of the Whispered Hope in the screenshot
- Field when warden is triggering: This is from the same point of time as the screenshot above, but with the battlefield view instead of the browser view