I think this is true because Lord Hanuman is Chiranjeevi and he was also found in the top of the chariot of Arjuna during the battle of Kurukshetra. But I can't understand what is the reason to stop the path of Bhima.
This is a test for Bhima to not be deceived by things that he is seeing and being careful with using his strength.
"Then knowing him (Bhima) to be intoxicated with strength, and proud of the might of his arms, Hanuman, slighting him at heart, said the following words, 'Relent thou, O sinless one. In consequence of age, I have no strength to get up. From pity for me, do thou go, moving aside my tail.' Being thus addressed by Hanuman, Bhima proud of the strength of his arms, took him for one wanting in energy and prowess, and thought within himself, 'Taking fast hold of the tail, will I send this monkey destitute of energy and prowess, to the region of Yama.' Thereat, with a smile he slightingly took hold of the tail with his left hand; but could not move that tail of the mighty monkey.