Looks to me that it got leggy indoors, which is why you moved it outside, right? Then it took advantage of the extra light and decided to grow new branches from all the nodes exposed to the light. I wouldn't worry about it. If it bothers you, you can always prune it in the late winter.

Ok, so that's what leggy looks like, lol.

So it's not supposed to look like that but it's perfectly fine if it does, awesome lol.

It's an aesthetic thing. Trim it back in the spring, put it outside and watch it really take off.

I would want to grow it as 'hard' as possible over the winter ie as cool as it will take and with plenty of light. That sappy anaemic leggy growth is going to be prey to any fungi and bugs going around and the plant really ought to be resting now, not trying to grow. I realise you can't put it outdoors but try to find a light cool place for it to tick over gently until spring. Then keep it outside as long as possible before it comes back in for the winter. Lavender is not well suited to an indoor life.

French/Spanish lavender does this sometimes. I have some types outside that do this, some are more upright. Sometimes even those who seeded themselves out of an upright plant do this...so who knows?