You know, this is actually true. The Elite Four levels of both, at least in DP, are also similar and progress in the same way with each Elite Four being two levels higher and then the Champion is three levels higher.
The only difference is DP Sinnoh's E4+Cynthia levels of their aces at least are exactly one level higher than the aces of RB Kanto's E4+Blue.
That's in addition to the level curves of the Gym Leaders being relatively similar too yeah, not to mention the first Gym is Rock and the second is a starter type with a very strong fully evolved Pokemon as the ace (Starmie or Roserade).
There are a few other parallels out there too. Namely Barry's team composition mirroring Blue's, using a FWG core including his starter and having two of three set Pokemon based on that, and always leading with the regional bird (Barry's Staraptor and Blue's Pidgeot). Staraptor itself was the first regional bird to actually closely follow Pidgeot's design ethos from a gameplay standpoint.
Uxie, Mesprit, and Azelf are also met at Level 50 like Articuno, Zapdos, and Moltres and pretty late into the game, and then both RGB and DP also unlock post-game dungeons that have you meet a Level 70 Legendary (Cerulean Cave's Mewtwo vs Turnback Cave+Stark Mountain Giratina+Heatran) after you beat the Champion.
I could go on and on there but there's seemingly a lot of mirrors between Sinnoh and Kanto in all sorts of places.
While not expressly a parallel there was one reference in DPP of some guard at a gate claiming to be thirsty which is an obvious shoutout to the Saffron guards.
The Kanto references actually run pretty deep and even earlier than most think, looking at it. Kanto's influence shows itself a lot even in earlier generations.