No problem, it doesn't feel like you are picking on me, and considering how to answer caused me to consider how to clarify my ruling. Thank you.
You want to jump a 45 foot gap. You have a maximum jump distance of 45 feet, and a movement speed of 30 feet. The way I see it, If you don't take the dash action, then you aren't actually moving fast enough at the end of your turn for your momentum to carry you through the rest of the jump. Like, disregard the rules framework for a moment, in the narrative reality the encounter is taking place in, you need to lead up to that 45 foot leap at a sprint, not a jog, jump spell or no jump spell.
An increase in jump distance isn't an increase in movement speed, it's a upper limit to how much of your movement speed you can use to travel in a particular mode. Just because you can jump 45 feet doesn't mean you will jump that far every time you jump. It's an upper limit.
And, anyway, it just comes off as a cheesy way of gaining an extra action. If you are jumping a 45 foot canyon and can end your turn in midair, you can take an action on the near side and an action on the far side. If you have to dash on the near side to make that jump in one turn, you only get an action on the far side.