Words are meant to communicate things through shared meaning and this is what seniority means to ~everybody else except you, so although nobody will stop you from adopting your private definition that nobody else uses, I think persistence in doing so will make you look a little silly.
The thing you're glossing over is Senior at Company A != Senior at Company B.
If your company wants to grossly inflate titles, fair enough - but your next job will then look like a demotion.
Counting someone as senior purely by a clock is also absurd. It's about knowledge, depth and breadth. A person with 3ish years of experience does not have either... we used to just call that "engineer".
