There are (5 C 2)*(3 C 2) = 30 two-pair combinations.

Now for the rank combinations: there are 13 ranks and we need 2 of them. 13 C 2 = 78

Each two-pair combination of specific ranks has the following probability:
(4^2 * 3^2 * 44) / (52 P 5) = 1 / 49222.7272…

Now for the final step:
P(dealt two-pair) = 30 * 78 * (1/49222.72…) = 198/4165

198/4165 is approximately 1/21.
To be exact, it’s 1 / 21.03535…
As a percentage, it’s 4.754%

So you heard correctly, and now you know how it was arrived at.